Neurobrucellosis: An Uncommon but Important Cause of Sensorineural Hearing Loss: a case report

Abstract

Background

Brucellosis is a zoonotic infection common in Mediterranean countries and the Middle East. Neurological involvement, although rare, can lead to severe complications, including sensorineural hearing loss (SNHL). This case is particularly noteworthy as it highlights irreversible auditory nerve damage in brucellosis, emphasizing the importance of early diagnosis and treatment to prevent permanent neurological consequences. The novelty of this case lies in the severity of auditory involvement despite timely treatment.

Case Presentation

A 43-year-old male farmer of Maghrebi origin presented with neurobrucellosis complicated by severe, irreversible bilateral sensorineural hearing loss. The patient initially reported symptoms of hearing loss and dizziness, which were confirmed to be associated with auditory nerve involvement. Wright’s serology and polymerase chain reaction (PCR) testing confirmed brucellosis. Despite appropriate and prolonged antibiotic therapy, including drugs that penetrate the meningeal barrier and act intracellularly, the patient’s auditory impairment remained permanent. The patient is currently a candidate for cochlear implantation to manage his severe hearing loss. Neurological symptoms did not improve with treatment, but cochlear implantation may offer a potential solution to his hearing deficit.

Conclusions

This case highlights the importance of early recognition and intervention in brucellosis cases, particularly those with neurological involvement. Delayed diagnosis and treatment can result in irreversible neurological damage. It also underscores the potential for cochlear implantation in patients with severe, irreversible sensorineural hearing loss caused by neurobrucellosis. Cochlear implantation offers an important solution for patients with brucellosis-related hearing deficits, improving their quality of life despite the neurological damage caused by the infection.

1. Introduction

First described on the island of Malta in 1859, brucellosis is a globally distributed zoonotic disease, predominantly affecting Mediterranean countries and the Middle East (Pappas et al., 2005; Dean et al., 2012). In regions where systematic eradication programs, including livestock vaccination, have been implemented, the disease has become rare. However, it remains a significant public health concern in endemic areas, particularly among individuals exposed to infected animals or unpasteurized dairy products (Malhi et al., 2015).

Neurobrucellosis, a severe but uncommon complication, presents with a wide spectrum of neurological manifestations, including meningoencephalitis, myelitis, cranial and peripheral neuropathies, and demyelinating syndromes. Among cranial nerve involvements, auditory nerve (VIII) damage is relatively frequent and may represent an early or even the primary clinical manifestation. Sensorineural hearing loss (SNHL), which can be unilateral or bilateral, is often accompanied by vestibular dysfunction, leading to dizziness and imbalance (Awada et al., 2011; Jabbour and Tabbarah, 2011). The underlying pathophysiological mechanisms remain uncertain but may involve direct bacterial invasion, immune-mediated responses, or vascular impairment.

Here, we report a case of bilateral SNHL associated with neurological dysfunction as a manifestation of neurobrucellosis, highlighting the importance of early recognition and intervention to prevent irreversible complications.

2. Case Presentation

2.1. Patient Information

We report the case of A.M., a 43-year-old male farmer of Maghrebi origin, admitted to the Neurology Department with tetraparesis, speech disturbances, and severe hearing loss.

2.2. Family and Psychosocial History

The patient is a 43-year-old male farmer from a rural area with regular exposure to livestock and consumption of unpasteurized dairy products. There is no family history of hearing loss or neurological disorders. The profound bilateral SNHL significantly impacted his social interactions and professional activities, leading to social isolation and reduced quality of life.

2.3. Clinical Findings

The symptoms began approximately three months prior to admission, initially presenting as balance disorders and headaches, for which he sought medical consultation and received symptomatic treatment. However, his condition did not improve, and he progressively developed significant hypoacusis. He was subsequently referred to an otolaryngologist, who initiated corticosteroid therapy, but with no significant clinical improvement.

Over the past month, the patient experienced worsening neurological symptoms, culminating in the onset of tetraparesis, prompting hospital admission. Clinical examination revealed a bilateral pyramidal syndrome, more pronounced in the lower limbs, characterized by increased muscle tone, reduced muscle strength (Medical Research Council grade 3/5 in the lower limbs), brisk deep tendon reflexes, and bilateral extensor plantar responses, along with a cerebellar static and kinetic syndrome

Audiological assessment included pure-tone audiometry, confirming severe bilateral sensorineural hearing loss with thresholds exceeding 70 dB HL across all tested frequencies. (Figure 1)

Figure 1.

Cross audiogram showing severe bilateral hearing loss in both ears across all tested frequencies. (Personal iconography)

Due to the clinical context and symptomatic severity, brainstem auditory evoked potentials (BAEPs) were attempted; however, no reproducible waveforms were obtained, indicating possible auditory nerve involvement (Figure 2).

Figure 2.

Pathological BAEPs recording from the patient, showing absence of reproducible waveforms (no detectable waves).

2.4. Diagnostic Assessment

Two brain magnetic resonance imaging (MRI) scans were performed but did not reveal any significant abnormalities. (Figure 3) and (Figure 4)

Figure 3.

Axial brain MRI (T1 and T2 sequences) with gadolinium contrast showing no significant abnormalities. (Personal iconography)

Figure 4.

Sagittal brain MRI (T1 and T2 sequences) with gadolinium contrast showing no abnormalities. (Personal iconography)

A blood test revealed an inflammatory syndrome, and lumbar puncture analysis showed cloudy cerebrospinal fluid (CSF) with pleocytosis (60 cells/mm³, 100% lymphocytic), marked hyperproteinorachia (2.86 g/L), and hypoglycorrhachia (0.25 g/L).

Serological tests for syphilis, hepatitis B and C, HIV, and Lyme disease were all negative. Upon thorough patient history taking—considering his occupation—a prior episode of undiagnosed febrile illness with profuse sweating was identified, occurring five months before admission and treated symptomatically. Additionally, dietary habits included the regular consumption of raw and unpasteurized goat’s milk products, a known risk factor for brucellosis.

To investigate a possible brucellosis infection, Rose Bengal and Wright’s serological tests were performed, both returning positive, with a Wright titer >1/320. These findings confirmed the diagnosis of neurobrucellosis.

2.5. Therapeutic Intervention

The patient was initiated on a triple antibiotic regimen comprising doxycycline (200 mg/day), rifampicin (900 mg/day), and trimethoprim-sulfamethoxazole (Bactrim, 4 tablets/day) for a total duration of six months, combined with corticosteroid therapy.

2.6. Follow-up and Outcomes

After six months of treatment, the patient showed moderate motor improvement, resolution of headaches, and normalization of cerebrospinal fluid (CSF) parameters. However, his hearing recovery remained incomplete, with persistent severe bilateral sensorineural hearing loss. The patient is now a candidate for cochlear implantation.

After one year, the patient's paresis had significantly improved, becoming minimal. However, the severe bilateral hearing loss persisted, with no functional improvement despite the use of hearing aids.

Detailed electrophysiological tests including auditory evoked potentials (AEP) suggested preserved retrocochlear and central auditory pathways, supporting the functional integrity of these structures.

These findings were critical in determining the patient’s candidacy for cochlear implantation, despite the profound hearing loss caused by neurobrucellosis.

A summary of the patient’s clinical course, investigations, treatments, and outcomes is presented in Table 1.

Table 1. Clinical Timeline.

Time (T)	Clinical Event and Investigations	Treatments and Interventions	Outcomes/Evolution
T = -5 months	Febrile illness with profuse sweating, undiagnosed	Symptomatic treatment	Partial resolution
T = 0	Initial consultation: balance disorders, headaches	Symptomatic treatment	No improvement
T = +3 months	Progressive bilateral hearing loss	Corticosteroid therapy (by ENT)	No improvement
T = +4 months	Hospital admission: tetraparesis, neurological signs	Triple antibiotic therapy (doxycycline, rifampicin, co-trimoxazole), corticosteroids	Motor improvement, hearing loss persists
T = +6 months	Neurological and audiological follow-up	Continuation of treatment, cochlear implant evaluation	Persistent severe bilateral SNHL
T = +12 months	Long-term follow-up	Cochlear implantation planned	Motor function improved, hearing loss unchanged

3. Discussion

Brucellosis is a globally distributed zoonotic disease, with a particularly high prevalence in Mediterranean countries and the Middle East. Brucella melitensis is the most pathogenic species for humans, with its primary reservoir being terrestrial mammals, particularly small ruminants such as goats and sheep (Pappas et al., 2005; Ben Hamouda et al., 2007).

The global incidence of brucellosis is estimated at approximately 500,000 new cases annually (Dean et al., 2012). In endemic regions, including Algeria, reported incidence rates range between 50 and 500 cases per 1,000,000 inhabitants (Figure 5) (Gul et al., 2009; Malhi et al., 2015).

Figure 5.

Global Incidence of Brucellosis (adapted from: Yousra M. Neurobrucellose: à propos d’un cas et revue de la littérature. Doctorate thesis in Medicine, Rabat, Morocco, 2018).

Neurological involvement in brucellosis is estimated to occur in 1.7% to 10% of cases and can manifest as meningoencephalitis, cranial and peripheral neuropathies—particularly involving the auditory and optic nerves—as well as demyelinating syndromes (Ben Hamouda et al., 2007; Gul et al., 2009; Awada et al., 2011).

Auditory nerve damage primarily presents as sensorineural hearing loss, which may occur with or without vestibular dysfunction, such as dizziness and balance disorders. In a reported series, 19 out of 23 patients exhibited sensorineural hearing impairment (Jabbour and Tabbarah, 2011; Malhi et al., 2015).

Recent studies confirm that neurobrucellosis continues to be a diagnostic challenge, especially in non-endemic areas, due to its protean manifestations and the lack of pathognomonic imaging findings (Colmenero et al., 2005; Soares et al., 2023). MRI is often normal, as in our case, but when abnormal, it may show meningeal enhancement, white matter lesions, or cranial nerve involvement. However, these findings are neither sensitive nor specific, and a normal MRI does not exclude the diagnosis (Al-Sous et al., 2004; Erdem et al., 2016).

The pathogenesis of nerve damage in neurobrucellosis is complex and multifactorial. Direct bacterial invasion of neural tissue, immune-mediated inflammation, and vascular compromise due to small-vessel vasculitis have all been described (Solís García del Pozo and Solera, 2012). Recent reviews suggest that persistent inflammation and cytokine-mediated injury may play a significant role in irreversible neural damage, particularly when diagnosis and treatment are delayed (Soares et al., 2023).

The isolation of Brucella species through culture remains challenging due to their slow growth and low sensitivity in cerebrospinal fluid samples. Therefore, diagnosis primarily relies on Wright’s serology, as recommended by the World Health Organization (WHO), along with PCR testing for increased sensitivity and specificity (Colmenero et al., 2005; Erdem et al., 2012).

The triple antibiotic therapy used in this case (doxycycline, rifampicin, and trimethoprim-sulfamethoxazole) is currently recommended for neurobrucellosis because all three agents have excellent intracellular penetration and are effective against Brucella spp. in the central nervous system (Ceran et al., 2011; Erdem et al., 2012). Recent guidelines emphasize the importance of prolonged treatment (at least 6 months) to reduce the risk of relapse and ensure eradication of the pathogen (Erdem et al., 2012).

Treatment consists of prolonged antibiotic therapy with agents capable of penetrating both the meningeal barrier and intracellular compartments, typically administered for at least six months (Gul et al., 2009; Awada et al., 2011). Early initiation of therapy is crucial, as delays in diagnosis and treatment increase the risk of irreversible neurological deficits (Patra et al., 2022).

In addition to diagnostic and treatment considerations, comprehensive audiological assessment is crucial for defining the location and extent of hearing loss, especially given the possibility of retrocochlear pathway involvement in neurobrucellosis (Erdem et al., 2012; Solís García del Pozo and Solera, 2012). In our case, pure-tone audiometry confirmed severe bilateral sensorineural hearing loss. We attempted auditory brainstem response testing, but reproducible waveforms could not be obtained, likely due to the degree of hearing loss. However, advanced electrophysiological testing including auditory evoked potentials indicated preserved retrocochlear and central auditory pathways, supporting the integrity of these structures. This distinction was essential in evaluating candidacy for cochlear implantation, as successful rehabilitation relies on intact neural transmission beyond the cochlea (Altuntaş et al., 2021; Patra et al., 2022).

Although SNHL due to neurobrucellosis can be irreversible despite adequate antibiotic therapy, cochlear implantation offers a promising option to restore auditory function and improve quality of life. Long-term outcomes are generally favorable, although the extent of nerve damage may limit maximal hearing recovery compared to other etiologies ( Altuntas et al.,2021). Recent case series confirm that cochlear implantation in post-infectious SNHL, including brucellosis, leads to significant improvements in speech perception and social integration, though some patients may have less optimal results if there is extensive neural damage (Altuntaş et al., 2021; Mirza et al., 2022).

The strategy of proceeding with cochlear implantation in this patient is further supported by the absence of retrocochlear or central auditory dysfunction. Our approach is consistent with the literature, which suggests that patients with profound sensorineural hearing loss and preserved retrocochlear integrity—despite negative ABR—can benefit significantly from cochlear implants (Patra et al., 2022; Ahmadian et al., 2024). In a recent series, Patra et al. reviewed 221 reported cases of neurobrucellosis, further highlighting the broad clinical spectrum and the potential for severe neurological sequelae, including sensorineural hearing loss (Patra et al., 2022).

Currently, the most effective strategy against brucellosis is prevention. This includes vaccination of livestock, culling of infected animals, routine serological surveillance, strict hygiene measures such as glove use and thorough handwashing for at-risk professionals, and pasteurization of dairy products. To date, no effective vaccine is available for humans.

4. Conclusion

This case emphasizes the importance of early recognition and treatment of neurobrucellosis, particularly in individuals with known risk factors such as consumption of unpasteurized dairy products. Despite appropriate antibiotic therapy, the patient experienced persistent severe bilateral sensorineural hearing loss, highlighting the potential for long-term auditory complications in neurobrucellosis. The case also underscores the need for alternative treatment strategies, such as cochlear implantation, for managing irreversible hearing loss. Early diagnosis and prompt intervention remain critical in preventing irreversible neurological damage, and this case further supports the need for continued awareness of brucellosis as a potential cause of neurological deficits in endemic regions.

5. Patient Perspective

The patient expressed that while the antibiotic treatment helped improve some neurological symptoms such as motor function and headaches, the persistent severe hearing loss has had a profound impact on his daily life, social interactions, and professional activities. He shared feelings of frustration and isolation due to the irreversible nature of his hearing impairment despite timely treatment. However, he remains hopeful that the upcoming cochlear implantation will restore some of his auditory function and significantly improve his quality of life.

Funding Statement

Not applicable.