Pathway of care for visual and vestibular rehabilitation after mild traumatic brain injury: a critical review

Abstract

Primary Objective:

To review the pathway to care for treatment and management of patients receiving visual and vestibular rehabilitation after mild traumatic brain injury (mTBI).

Methods & Procedures:

English scientific peer-reviewed articles from PubMed, CINAHL, Embase, and PsycINFO between 2000 and 2020 were first screened by title and abstract, then those selected underwent full-text review and analysis.

Main Outcomes & Results:

The database search yielded 1640 results and after title and abstract review, 75 articles were selected for full-text screening, from which 8 were included in the qualitative synthesis. Current evidence includes a limited number of retrospective cohort studies and case studies.

Conclusions:

Many patients with visual and vestibular deficits following mTBI do not receive rehabilitation services until months following their injury as there is no standardized pathway to care for patients for visual and vestibular rehabilitation. Barriers to establishing a standardized pathway are the lack of natural history data for visual and vestibular function following mTBI and the lack of randomized clinical trials establishing the efficacy of rehabilitation in patients following mTBI.

Introduction

Traumatic brain injury (TBI) is one of the most common causes of disability and mortality worldwide among trauma-related injuries (1) and is a serious public health concern. Globally, an estimated 42 million people suffer a mild traumatic brain injury (mTBI) or concussion every year (2), accounting for up to 70–90% of all hospital-treated brain injuries (3). Approximately 100–300 people per 100,000 population worldwide receive medical care for mTBI annually (3).

Commonly referred to as the ‘silent epidemic,’ 70–90% of TBI cases are classified as mild among civilians (4), as the diagnosis is largely based upon functional rather than structural brain impairment. While the term ‘mild’ refers to the extent of the brain injury, the term ‘mild’ does not refer to symptom severity as symptoms are often debilitating and result in prolonged functional impairment (5). A recent meta-analysis on the clinical presentations of concussion, a term often used interchangeably with mTBI (2), divided the clinical presentations into five phenotypic subtypes: cognitive, ocular-motor, headache/migraine, vestibular, and anxiety/mood, and two associated conditions: sleep and cervical (6). Of these five subtypes, ocular-motor and vestibular symptoms were found to be significantly worse in concussion patients than in controls in both pediatric and adult patients (6,7).

The ocular-motor subtype is characterized by deficits in ocular motility, accommodation, vergence, the vestibular-ocular reflex (VOR), and visual perceptual skills (6). The vestibular subtype is defined as dysfunction associated with body movement and orientation/position detection causing dizziness, nausea, vertigo, disequilibrium, etc., symptoms often initiated by dynamic movement (6). The vestibulospinal and vestibulo-ocular components play an essential role in balance, gaze stabilization, and visual and spatial orientation by detecting head motion and maintaining retinal image stability (8,9). Vestibular system disruptions from a mTBI may result in balance and/or gait difficulties. Symptoms resulting from visual and vestibular dysfunction are often found in the same patient population and are increasingly grouped together as visuo-vestibular symptoms (Figure 1). The synergistic visual and vestibular system interaction helps to preserve gaze and postural stability during movement by providing continuous spatial orientation and positional feedback (10). Due to the mismatch between the visual and vestibular systems, patients may experience symptoms such as unsteadiness, feeling bothered by dynamic moving environments (e.g., walking through aisles in a grocery store or while traveling in a moving vehicle), dizziness, and nausea and blurriness while reading, etc. (11).

Figure 1.

Common Visual and Vestibular Symptoms Experienced Post-mTBI.

Emerging evidence indicates that visual and vestibular symptoms remain persistent in some individuals, among which, balance instability and dizziness symptoms are associated with an incidence rate of 30% to 80% regardless of TBI injury mechanism or severity, and that these symptoms prolong recovery after mTBI, especially in children (10,12-18). In particular, visuo-vestibular deficits are often persistent symptom contributors among the 30% to 88% of individuals whose concussion symptoms do not resolve within two weeks (12,19,20). In a recent retrospective study of college athletes with mTBI following blunt head trauma during varsity sports, abnormal vestibular and oculomotor assessments were found to be more common than reports of abnormal auditory symptoms (21). Approximately 60% of athletes in a separate cross-sectional study were found to experience both oculomotor and vestibular impairments following sports-related concussion (22). Concomitant visual and vestibular disturbances may also contribute to cognitive difficulties in some cases (23).

Rehabilitation for patients with mTBI requires a multidisciplinary team to generate a comprehensive treatment plan and to manage the multi-system impacts of head trauma (24). Vision and vestibular rehabilitation are related approaches which use eye and balance exercises targeting the vision and vestibular systems, respectively, to resolve these symptoms (25). Recent reviews have described mTBI pathophysiology and diagnosis, as well as the evolution of mTBI assessment (26). While many have reported the importance of vision therapy (27,28) and vestibular therapy (8,13,19,29-31) services separately in the rehabilitation plan for mTBI patients, to date, no reports have explained how these services are organized and how patients navigate through the healthcare system to receive visual and vestibular care. Patients presenting with visuo-vestibular dysfunction and impairments following a mTBI may be categorized under both the ocular-motor and vestibular subtypes (6), thereby making the pathway to care more complex. There is a growing need to better understand what vision and vestibular rehabilitation services entail (procedures, goals, and treatment strategies), which professionals provide those services (optometrists, ophthalmologists, physical therapists, occupational therapists, athletic trainers, etc.), and how to co-manage these patients in a multidisciplinary approach such that patients can receive comprehensive care.

We describe and synthesize the existing literature on the current visual and vestibular rehabilitation service delivery models post-mTBI and outline areas in which these two forms of rehabilitation may complement each other. Our post-mTBI management perspective focuses on reducing the prolonged visual and vestibular dysfunction duration to improve outcomes.

Methods

English scientific peer-reviewed articles from PubMed, CINAHL, Embase, and PsycINFO between 2000 and 2020 were reviewed. The developed search strategy was implemented on December 28, 2020, containing four topics and its derivatives: mTBI, vision rehabilitation, vestibular rehabilitation, and care/service delivery (Table 1). Articles were first screened by title and abstract by one reviewer (author LX) then selected for full-text review and synthesis then verified by a second reviewer (author SB). Any disagreement between the two reviewers at the full-text stage would be settled through discussion and adjudication with a third reviewer (author AW). Articles were included only if they reported a care delivery pathway or referral care model for patients with visual and vestibular deficits post-mTBI. Articles were excluded if the article solely described condition prevalence post-mTBI or treatment studies in the absence of including information on the care delivery pathway. Review articles and conference papers were also excluded.

Table 1.

Search Strategy.

TBI (Head Injury)

(traumatic brain injur* OR mild traumatic brain injur* OR brain injur* OR concussion* OR brain trauma* OR neurotrauma* OR head trauma* OR (brain AND injury))

AND

Vision Rehabilitation (Visual Deficits)

(vision* OR vision loss* OR vision disorder* OR vis* impairment* OR vis* deficit* OR eye disorder* OR eye impairment* OR eye deficit* OR “vision rehabilitation” OR vis* rehabilitation* OR (vision AND rehabilitation) OR “vision therapy” OR vis* therap* OR neuro-optometric vision rehabilitation OR binocular vision OR vergence OR convergence OR version OR alignment OR ocular motor dysfunction OR ocular-motor impairment* OR ocular-motor* OR accommodation OR ocular motility OR optometr* OR neuro-optometr* OR ophthalmolog*)

AND

Vestibular Rehabilitation (Vestibular Deficits)

(“physical therapy” OR physical therap* OR physical rehabilitation* OR vestibular rehabilitation* OR vestibular dysfunction OR vestibular impairment OR vestibular therap* OR vestibular* OR gait deficits OR balance deficits OR balance impairment* OR musculoskeletal impairments)

AND

Healthcare Management

(healthcare service* OR service delivery OR service delivery model* OR organization of service* OR management OR strateg* OR approach OR team approach OR rehabilitation OR care OR transitional care OR transition OR model OR framework OR guideline OR integrat* OR coordinat* OR collaborat* OR interdisciplinary collaborat* OR multidisciplinary collaborat*)

Results

The scientific database search (MEDLINE via PubMed, CINAHL, Embase and PsycINFO via Ovid) yielded 1640 total results. Following an initial title and abstract review, 75 articles were selected for full-text screening, of which 8 were included in the qualitative synthesis. (Figure 2) There were no disagreements between the two reviewers at the full-text stage and classification.

Figure 2.

PRISMA Diagram Outlining Literature Search Method.

Summary of evidence

Multiple healthcare delivery and care pathways and models for this population were identified, consisting of both sequential and combined treatment management (Table 2).

Table 2.

Summary of Evidence.

Reference	Article Type, Level of Evidence	Sample Characteristics + Size (N), Outcomes	Intervention Pathway	Key Findings, Results & Conclusion
Near Point of Convergence after Concussion in Children (Storey et al 2017)	Retrospective Cohort Study, Level 2b	n = 275 children (age 5–18) presenting with concussion, home exercise program administered typically 1–2 weeks after presentation	Standard clinical care for median time frame of 4.5 weeks, then vestibular therapy if symptoms persist beyond 4 weeks, then vision therapy if symptoms persist following full course of vision therapy	Of 67 who were assessed to have abnormal NPC, 56 patients resolved, of which 26 (46%) recovered with standard clinical care, 23 (41%) with vestibular therapy, and 7 (13%) with vestibular and vision therapy. Standard care in the concussion program: For patients with persisting vestibular or visual problems lasting >4 weeks = > referral for formal vestibular physical therapy, consisting of standard habituation exercises for vestibular symptoms and balance training, and convergence exercises such as Brock string and pencil pushups. Patients with persisting abnormal NPC >8 to 12 weeks after injury = > referral for a formal developmental optometry evaluation & vision therapy.
Vestibular Rehabilitation Is Associated With Visuovestibular Improvement in Pediatric Concussion (Storey et al 2018)	Retrospective Cohort Study, Level 2b	n = 109 children (mean age = 11.8 years) diagnosed with concussion within 1 year of injury, 59 (54%) were male, 48 (44%) had a sports-related concussion, of which 45 participated in some form of physical therapy.	Vestibular rehabilitation if symptoms persist beyond 3 weeks	Children completed therapy in a median of 7 visits; over a median duration of 56 days # of concussion symptoms decreased from median 9 initially to 0 at final assessment. Visuo-vestibular symptoms decreased from 70.1% at initial presentation to 20% after vestibular therapy sessions. Participation in PT significantly increased mean level of performance on the Balance Error Scoring System (p < 0.0001). Reasons for nonadherence to recommended PT: wide and varied in scope, including insurance reasons, referral to vision therapy, or missed discharge assessment. Important potential role for targeted vision rehabilitation to address the deficits that persist after vestibular PT, which may partially account for the subset of children (24%) with lingering symptoms following vestibular PT.
Head-Eye Vestibular Motion Therapy Affects the Mental and Physical Health of Severe Chronic Postconcussion Patients (Carrick et al 2017)	Retrospective clinical chart review at Institutional Brain Injury Clinic (Tertiary Specialist Brain Rehabilitation Center), Level 2b	n = 70 subjects w/ post-concussive syndrome w/ severe impairments for >6 months after mild TBI (age: 14–47 y.o., mean age for males = 28, females = 29) intervention: HEVM therapy + underwent comprehensive neurological examinations including measurement of eye and head movement.	5 day HEVM therapy: 1) gaze stabilization exercises administered with coordinated HEVM at positions & speeds associated with a decomposition of head & eye tracking movements = > 5 times/day with 1.5 h rest between sessions vestibular & somatic stimulation administered by placing patient in an accelerated rotation in a multiaxis rotational chair (MARC) = > 2 sessions/day somatic sensory motor movements involved subject complex movements of upper & lower extremity, both passively with therapist & actively (right arm, left arm, right leg, and left leg) & in combination (right arm-left leg, left arm-right leg, right arm-right leg, and left arm-left leg) = > 3 sessions/day	No statistically significant differences between males & females before and after 5 day HEVM treatment Statistically significant decrease in symptom severity scores [post-blurred vision (p = 0.036), post-don’t feel right (p = 0.044), post-orientation, post-concentration (p = 0.000)] associated with chronic PCS after HEVM treatment with a large effect size (Cohen’s d = 0.83)
Improvement of Saccadic Eye Movements After Head-Eye Vestibular Motion (HEVM) Therapy and Neuro-Psychiatric Considerations (Carrick et al 2019)	Single center, retrospective review of records of the Institutional Brain Injury Clinic, Level 2	n = 154 subjects with post-concussion syndrome (>6 months) and mental health issue, 91 males and 63 females with mean age of 36.73 years (SD = 21.58, minimum age = 5 years, maximum age = 91 years) outcome: measurements of saccadic movement taken before and after HEVM therapy	5-day HEVM therapy (see above)	No difference between male and female performance = > combined in the analysis Measurements of saccadic movement taken before and after 5-day HEVM therapy show statistically significant and substantive improvement
Technology-enhanced visual desensitization home exercise program for post-concussive visually induced dizziness: a case series (Hurtado et al 2020)	Case Series, Level 4	n = 23 subjects (mean age 23.1 ± 12.4) with post-concussive dizziness (mean 109 ± 56 days post-injury) and no evidence for peripheral vestibular dysfunction	Combination of conventional vestibular rehab therapy and a technology-enhanced visual desensitization home exercise program (HEP) = > Treatment duration averaged 6.9 ± 2.5 weeks	Significant improvements in postintervention on subjective and objective measures of dizziness and gait (p < 0.05). The combination therapy intervention improved outcome measures consistent with VRT treatment outcomes in both concussion and non-traumatic vestibular conditions.
Combined Optokinetic Treatment and Vestibular Rehabilitation to Reduce Visually Induced Dizziness in a Professional Ice Hockey Player After Concussion: A Clinical Case (Mucci et al 2019)	Case Study, Level 5	25 y.o. pro hockey player underwent 5-day combined vestibular, balance and optokinetic therapy after multiple concussions = > remission of VID symptoms (within short time frame after last concussion)	5-day combined vestibular, balance & optokinetic therapy consisting of 1 h vestibular/ocular-motor exercise training & 45 min session of exposure to optokinetic stimuli combined with postural control exercises over 2 weeks On “rest” days, instructed to perform exercises at home (page 2).	Patient was able to return to ice hockey 15 days after the final treatment session and reported no symptoms in the 3 month follow up questionnaire. Potential benefit of treating post-concussive VID symptoms utilizing a multi-modal approach (the combination of vestibular, balance and optokinetic therapy)
Visual-Vestibular Interaction and Treatment of Dizziness: A Case Report (Brennan, 2012)	Case Study, Level 5	52-year-old female post-TBI from car accident (closed head trauma) resulting in visual and vestibular dysfunction	Physical therapy (vestibular), Occupational therapy & in-office Vision therapy at 17 months post-accident for 5 months, then 6 weeks of physical therapy (vestibular) at 26 months post-accident	Following vision therapy (6 months after the car accident), patient reported significant improvements in everyday activities & quality of life = > more stable vision, improved balance, improved comprehension and ease with reading Prior recommendation for inner ear surgery from ENT was retracted following significant balance improvements from vision therapy Demonstrates how rehabilitative vision therapy leads to alleviation of visual-vestibular symptoms & highlights the “necessity for collaboration between various professionals involved in the rehabilitation process to bring about the best possible outcome for the patient” (page 72).
Application of a Mild Traumatic Brain Injury Rehabilitation Program in a Virtual Reality Environment: A Case Study (Rabago & Wilken, 2011)	Case Study, Level 5	31-year-old male service member sustaining post-mTBI during a recreational softball game evaluated in a VR system 36 days post-injury by a physical therapist, complaints of severe visual & physical motion intolerance outcome: measurements of postural and gait balance during cognitive, visual, and vestibular challenges within a Computer-Assisted Rehabilitation Environment	Six 1-h Vestibular therapy treatments over 3 weeks Phase 1: clinical techniques (ie, optokinetic stimulation/habituation, visual/physical perturbations, & postural stability exercises) targeting specific impairments Phase 2: weapon handling and target recognition tasks to simulate requirements of his military occupation	Demonstrated significant increases in postural and gait balance with a near complete resolution of all post-concussion symptoms Successfully returned to full duty and training for combat deployment Rehabilitation program in a virtual-reality environment can potentially manage complex mTBI symptoms through the integration of multiple treatment modalities

Sequential treatment care models

Two retrospective pediatric patient post-concussion cohort studies highlighted a clinical course where patients underwent standard clinical care for several weeks, after which a referral to vestibular therapy was made if visual and vestibular-related symptoms and deficits persisted, and then a subsequent referral to vision therapy if these symptoms were present following vestibular therapy (19,32).

In the first retrospective cohort study of 275 pediatric patients, of which 67 experienced receded near point of convergence, patients first underwent standard clinical care for a median of 4.5 weeks, during which 26 (46%) patients recovered (32). Standard clinical care was defined as a period of physical and cognitive rest for symptom reduction followed by a stepwise return to cognitive and physical activity as per previously published return-to-learn and return-to-play guidelines. Additionally, during the first month following the injury, a home exercise program that included saccadic and gaze stability exercises, pencil push-up and Brock string convergence exercises was prescribed 1 to 2 weeks after injury in some patients. If patients had persistent visual or vestibular problems after 4 weeks post-injury, they were referred for formal vestibular therapy that consisted of habituation exercises for vestibular and balance training, and Brock string and pencil push-ups for convergence training. A subsequent referral to formal vision therapy was made for patients with persistent abnormal near point of convergence (NPC) and concomitant symptoms if they were not abated following vestibular therapy. Twenty-three (41%) patients with persisting vestibular or visual symptoms recovered following the referral to formal vestibular therapy within a median of 11 weeks post-injury. An additional seven (13%) patients did not recover with vestibular therapy alone and were referred to vision therapy. Those seven patients recovered within a median of 23 weeks post-injury. By the end of the clinical care course, a total of 89% of patients with abnormal NPC resolved in a median of 10 weeks after injury and were deemed to benefit from interventions including vestibular or vision therapy (32).

In the second post-concussion cohort study of 109 pediatric patients, a referral to vestibular physical therapy was made based on visuo-vestibular examination if visuo-vestibular deficits continued more than 3 weeks post-injury (19). Upon initial examination, all children referred for visuo-vestibular therapy had visuo-vestibular dysfunction signs upon examination of which 70% (77 of 109) reported at least 1 visuo-vestibular symptom. 56.0% (61 of 109) of children presented with dizziness, 56.0% (61 of 109) with balance problems, and 42.2% (46 of 109) with vision problems (abnormal convergence or abnormal accommodation). Those referred to vestibular rehabilitation experienced decreases in visuo-vestibular symptoms from 70.1% at initial presentation to 20% following vestibular rehabilitation. The authors acknowledged that the subset of children (24%) with persisting visual symptoms following vestibular physical therapy may have benefited from vision rehabilitation (19).

A case study of a 52-year-old female who suffered a TBI from a car accident resulting in visual and vestibular dysfunction had sequential physical therapy followed by vision therapy and then an additional course of physical therapy (33). She completed her first course of physical therapy immediately following the accident to address her vestibular symptoms, which did not resolve completely. She was being seen by an ear, nose and throat (ENT) specialist at the same time, who then referred her for vision therapy and recommended exploratory inner ear surgery. At her initial vision therapy evaluation 17 months after the car accident, she was also undergoing occupational therapy treatment. She began a course of in-office vision therapy to address deficits in gross and fusional vergence and visual-spatial skills. Following her first month of vision therapy, the ENT specialist no longer recommended inner ear surgery since the patient’s balance test scores improved significantly. Following the five-month course of vision therapy, the patient reported that most of her vestibular symptoms had resolved except for continuing to feel off-balance when walking through a crowd. Her Keystone Visual Skills Test performance were normalized resulting in significant self-reported improvements in daily activities. She was then given a home maintenance therapy program for one month which included at home gross and fusional vergence and spatial coordination activities to be performed two to three days per week. Weeks after the cessation of home maintenance vision therapy, she was referred back to physical therapy for 6 weeks to address her residual vestibular symptoms. At her final vision therapy follow-up visit that followed her second course of physical therapy, a total of two years and four months following the initial car accident, her Keystone Visual Skills and binocular fusion ranges were stable and normal. The patient reported a decrease in symptoms in a crowd and no dizziness, after which she was discharged from vision therapy.

Combined treatment care models

Several retrospective chart reviews and case studies described combined approaches to post-TBI visuo-vestibular care.

In the first retrospective chart review of 70 patients (ages 14–47 years old) with post-concussive syndrome suffering from severe impairments for greater than 6 months after mild TBI, with the majority of these patients having undergone previous combinations of rest, rehabilitation, and pharmacological treatment, a 5-day intensive head-eye vestibular motion (HEVM) therapy program was prescribed (34). The HEVM therapy program included a three part treatment: 1) gaze stabilization exercises coordinated at head positions of pitch, yaw, and roll, and speeds associated with head and eye decomposition tracking movements performed for 3 minutes and repeated three times with a 3-minute rest break, which was repeated five times a day with a rest period of a minimum of 1.5 hours in between sessions, 2) vestibular and somatic stimulation sessions in a multi-axis rotational chair with 3–30 second acceleration-deceleration phases repeated twice a day with a 2-minute break between rotations, and 3) Passive and active somatic sensory motor movements three times a day (34). The program was found to significantly decrease patients’ mental and physical health symptom severity scores (34).

A second retrospective chart review of 154 patients (mean age of 36.73 years) with sport-related post-concussive syndrome and concurrent depression suffering from severe impairments for greater than 6 months showed significant improvement in saccadic eye movement after the same 5-day HEVM therapy program (35).

A combined optokinetic and vestibular rehabilitation approach was used to treat a 25-year-old hockey player experiencing visual and vestibular impairment causing visually induced dizziness, blurred vision, nausea, fatigue, and sensitivity to light following a history of three concussions (36). The player began treatment 20 days following his most recent concussion and was able to return to play in 15 days after the 5-day combined therapeutic treatment. In a follow-up questionnaire 3 months following treatment, the player reported no residual symptoms. The authors emphasized the importance of treating post-concussive visually induced dizziness symptoms with a multi-modal approach (36).

In a second case study, a 31-year-old male service member experiencing severe visual and physical motion intolerance following a concussion was first evaluated at the emergency department where he was given medication for a headache and swollen eye (37). He was then transferred to the Brooke Army Medical Center 9 days after injury when his initial symptoms of slurred speech, forgetfulness, headache, and vertigo/dizziness worsened. An evaluation by an occupational therapist was conducted 15 days after injury to address his symptoms of dizziness, vertigo and blurred vision worsened by riding in elevators, walking in stairwells and in crowds, after which he received 2 weeks of conventional vestibular rehabilitation. He was then referred to the Military Performance Laboratory for specialized physical therapy treatment using virtual reality after his motion sensitivity score increased following the course of vestibular rehabilitation. He was treated 36 days following the concussion with the use of virtual reality computer-assisted rehabilitation environment combined with clinical techniques (optokinetic stimulation/habituation, visual/physical perturbations, and postural stability exercises) during six 1-hour vestibular therapy treatments over 3 weeks. This treatment significantly increased postural and gait balance and nearly completely resolved severe visual and physical motion intolerance symptoms post-mTBI and aided his return to full duty and combat training for deployment (37).

In a recent case series, 23 individuals (mean age 23.1 ± 12.4) with post-concussive visually induced dizziness (VID) (mean 109 ± 56 days post-injury) with no peripheral vestibular dysfunction were evaluated by an oto-neurologist and then referred directly to a tertiary balance center (38). Therapy consisted of a combination of conventional vestibular rehabilitation therapy and a technology-enhanced visual desensitization home exercise program with an average duration of 6.9 ± 2.5 weeks was found to improve subjective and objective measures of dizziness and gait (p < 0.05).

Discussion

Despite there being many publications dedicated to pathophysiology of mTBI and symptomatology, there is a paucity of information relating to post-mTBI visuo-vestibular treatment pathways and care delivery models, specifically for prolonged visual and vestibular symptoms and disorders. The current state of evidence includes a few retrospective cohort studies and a limited number of case studies, which reflects an urgent need to establish treatment pathways and standardized care delivery models. In fact, none of the eight studies included in this review are comparable to a well-performed randomized trial due to high selection bias from the small sample sizes and would not provide any useful evidence for clinicians until further research is performed. The studies would be at critical risk of bias as per the Cochrane ROBINS-1 tool (39). Higher quality research in this area is needed as reflected by the few studies and small number of patients included in this review.

A thorough screening of the visual and vestibular systems should be performed for individuals sustaining a mTBI during the review of systems, including an assessment of the impairments resulting from the interaction between these systems and its functional relevance to movement (10,40,41). However, a critical barrier is that a standardized assessment has yet to be adopted. A recent scoping review outlining the most commonly used assessments for vestibular and ocular/oculomotor assessment following sports-related concussion and their efficacy found the Vestibular-Ocular Motor Screening Test (VOMS) to have strong reliability and validity, and the Gaze Stabilization Test (GST) to be promising in identifying patients with sports-related concussion and in predicting those at risk of prolonged recovery (42). However, the authors of the review noted that all reported studies included only pediatric, adolescent and young adult populations, revealing an area for further investigation in the adult population (42). Additionally, patients presenting with persistent post-concussion symptoms and receded near point of convergence (sub-test of the VOMS) should undergo a complete sensorimotor evaluation to determine the most appropriate treatment, as a receded near point of convergence is found in vision deficits other than convergence insufficiency (43). Furthermore, the VOMS and GST do not assess accommodation, a visual function that is commonly reduced in patients post-mTBI (7,43). An evidence-based screening protocol is needed so managing clinicians can be proactive in identifying visuo-vestibular deficits in patients post-mTBI due to its important implications for return-to-learn, return-to-play, and return-to-work decisions (19).

After the initial screening process, patients must be referred to the appropriate specialists to receive targeted and individualized care. Similar to the lack of standardization for a visual and vestibulo-ocular screening protocol to be used in a primary care setting, a major limitation in treating these patients is that there is no standardized approach to caring for this population and there are no randomized clinical trials to validate current treatment protocols, which may be due to the heterogeneous nature of mTBI. Furthermore, a patient’s functional outcome and treatment duration may likely be affected by which rehabilitation specialist they encounter first. Nonetheless, treatment for visuo-vestibular impairments should incorporate exercises that facilitate the interaction and functional integration between these two systems (10,44). Vestibular therapists, physical therapists, and vision therapists often incorporate exercises that overlap into each subspecialty despite the emphasis of their targeted treatment in their own discipline and only refer the patient to the respective sub-specialty if significant deficits are present or symptoms persist (13). Patients experiencing chronic visual dysfunction in combination with a decline in ocular and overall health after TBI may benefit from both formal vision rehabilitation and vestibular physical therapy (40,45).

The pathways of care in the retrospective cohort and case studies suggesting that a referral to vestibular therapy be performed before vision therapy may potentially be attributed to patients, especially children, not recognizing visual symptoms on their initial physical examination when there are underlying visual deficits (19). Symptoms due to vision deficits are also not comprehensively elicited during initial examinations. For example, the Post-Concussion Symptom Scale (PCSS) (46) is a symptom survey commonly used to assess a wide range of symptoms post-mTBI but only includes two questions regarding vision, ‘blurred vision’ and ‘sensitivity to light.’ This may delay the incorporation of vision specialists on the post-mTBI care team. The inclusion of vision care providers is important, however, as a recent report has shown that symptom score on the PCSS are correlated with vision symptoms (20) assessed using the Convergence Insufficiency Symptom Survey (47), a survey dedicated to assessing a wide range of symptoms specific to vision. Despite the importance of including vision care providers, it is unknown if addressing patients’ visual deficits earlier in the treatment plan through a combined vision rehabilitation and balance therapy approach would be more effective in reducing or resolving these symptoms since the vestibular system relies on an intact oculomotor system (10,18). Impaired vision will negatively impact the vestibular rehabilitation process, as sustained clear and single vision is required for active participation in physical and vestibular therapy, in particular, for ambulation in a complex environment (23,48). Patients resolving visual problems through vision rehabilitation have reported a decrease in the severity of their vestibular symptoms (49).

The UPMC Sports Concussion Program in Pittsburgh highlights a model whereby patients undergo an initial comprehensive evaluation with a neuropsychologist, after which referrals to vestibular therapy, vision therapy, neurosurgery, etc., are made (50). The authors note that the leading role of the neuropsychologist could be served by other qualified professionals, such as neurosurgeons, neurologists, sports medicine physicians, and primary care physicians (50).

Roberts et al. (2016) identified that vision specialists (ophthalmologists, optometrists, and others who specialize in vision rehabilitation) are sometimes initial consultants in post-TBI care and integrated into the traditional interprofessional rehabilitation team with physicians, nurses, physical therapists, occupational therapists, etc., at a later stage in the treatment plan even though all members of the rehabilitation team address vision directly or indirectly in a broader context. Since non-vision clinicians frequently make first contact with an individual after a mTBI, the authors highlight an integrated care model where frontline non-vision clinicians collaborate and communicate with vision specialists to identify the vision impairment and connect the associated dysfunction to visual function for optimal comprehensive assessment and therapeutic remediation (51).

An additional barrier to optimal care is that the natural history of visual and vestibular disorders following mTBI is unknown. Thus, the ideal timing for the delivery of interventions, follow-up assessments, and referrals for patients post-mTBI thus far is also unknown. A retrospective cohort study of 432 patients (age range of 5 to 18, median 14 years old) referred to a subspecialty pediatric concussion program within one year of the injury found that visual and vestibular dysfunction prolonged concussion recovery regardless of whether patients presented to the concussion program within or beyond 14 days of injury (12). A 3-year prospective observational study evaluated the initiation and frequency of rehabilitation services in all TBI severities for the first 8 days following admission to an urban Level 1 trauma hospital; however, the authors concluded more research is needed to link the timing and frequency of these services to patient outcomes (52). Different injury and recovery assessments may be needed at various stages of recovery. Until the natural history is understood, it is difficult for practitioners to understand the ideal timing and implications for patient assessment and treatment, and to identify when the trajectory changes and how to adjust an intervention accordingly. Further research is needed to determine at which stage of recovery assessments are needed and to explore the diagnostic and treatment implications of assessment at various stages during the natural course of the injury.

Lastly, the evidence on rehabilitation strategies for both oculomotor and vestibular impairment and symptoms necessitating the combined use of visual and vestibular therapy following concussion is limited (8). Prospective investigational randomized studies are needed to assess the efficacy of each care pathway, and to determine when and how active vision and vestibular therapy treatments can be implemented to optimize recovery from mTBI (19,53).

Currently, visuo-vestibular deficits post-mTBI are treated separately by vision specialists (ophthalmologists and optometrists) and physical or vestibular therapists. Ongoing development of combined visuo-vestibular treatment approaches are also being documented independently in the literature through case studies, yet its efficacy and applicability to the general mTBI population still needs to be determined. Improved collaboration and cooperation between these specialties would stimulate integration of these rehabilitation services and may promote better patient outcomes.

Limitations

Although all articles across four databases from the last two decades were screened, this study has several limitations. As mentioned above, our study yielded only eight studies, three of which were case studies, which results in a high risk of bias. Also, the methodologies and interventions used in the eight studies included studies that are not validated, demonstrating a need for continued investigation on the topic. Patients with moderate or severe TBI were excluded from this study, as the management of these patients differ substantially from those with mTBI due to their complex and heterogeneous treatment needs (54). Due to the limited evidence that met our inclusion criteria, care delivery for different age groups was not differentiated, though all patients in the included articles were under the age of 55 except for the retrospective chart review article of HEVM therapy. It is possible that youth post-concussion or post-mTBI may benefit from different care pathways due to differences in brain development as compared to the adult population (55,56).

Conclusion/Future direction

This review of pathways to care for patients presenting with visual and vestibular deficits post-mTBI is an important step to continued investigation on the topic. The lack of understanding of the natural history of visuo-vestibular deficits post-mTBI and the paucity of studies assessing the efficacy of treatment for prolonged visuo-vestibular are barriers to establishing organized and effective care pathways. However, several retrospective studies, case studies, and case reports illustrate that with symptom management through treatment and rehabilitation, patients with mild TBI have potential to recover and return to work, sport, school, leisure, activities, etc. Further study is needed to better understand the critical gaps in natural history and efficacy of treatments of visuo-vestibular deficits to build on the principles and models reported in this review to establish pathways to care and standard care delivery models.