Compressive lesions of the head and neck: Common and uncommon must-know entities

Abstract

There are many lesions that cause compression of nerves and vessels in the head and neck, and they can often be overlooked in the absence of adequate history or if not suspected by the radiologist. Many of these lesions require a high index of suspicion and optimal positioning for imaging. While a multimodality approach is critical in the evaluation of compressive lesions, an MRI utilizing high-resolution (heavily weighted) T2-weighted sequence is extremely useful as a starting point. In this review, we aim to discuss the radiological features of the common and uncommon compressive lesions of the head and neck which are broadly categorized into vascular, osseous, and miscellaneous etiologies.

Introduction

There are many lesions that can cause compression of nerves and vessels of the head and neck, and many of these can be overlooked if not suspected by the radiologist or proper symptoms are not provided in the history. In addition, patients may not have symptoms in the neutral position but may experience symptom provocation in certain positions; therefore, it is important to perform imaging with the patient in the specific position that causes the symptoms, or the lesion may be missed. The purpose of this review is to discuss the common and uncommon compressive lesions of the head and neck, including potential mimics due to intrinsic pathology. These can be broadly categorized into vascular, osseous, and miscellaneous etiologies.

Vascular etiologies

Trigeminal neuralgia

Trigeminal neuralgia (TN) is characterized by paroxysmal unilateral orofacial pain in the distribution of the facial or intraoral trigeminal nerve territory. ¹ The pathognomic pain, often described as sudden brief stabbing or electric-shock like attacks can be triggered by maneuvers including innocuous mechanical stimuli, facial or oral movements, or complex activities such as shaving or applying make-up. These symptoms may be elicited on physical examination as well.^1,2 Classical TN is a specific category of TN wherein there is evidence of vascular compression either demonstrated on MRI or intraoperatively during neurovascular decompression, along with morphological changes within the trigeminal root.^1,3 Most vascular compressions in classical TN occur at the transitional zone (TZ) which is the microscopic region where the nerve sheath transitions from central myelin to peripheral myelin and is most vulnerable to compression.^4–6 The offending vessels in classical TN from most common to less common include the superior cerebellar artery, anterior inferior cerebellar artery, basilar artery, and petrosal vein.^7,8

Imaging

A pre-contrast CT of the head may be normal. A post-contrast CT of the brain and skull base is helpful in cases of secondary TN, such as sinus masses, cerebellopontine angle (CPA) masses, and skull base lesions. CT angiogram of the head can help evaluate vascular anatomy, such as ectasia or dolichoectasia of the vertebrobasilar system, but cannot demonstrate neurovascular compression. The best imaging tool is an MRI with high resolution sequences such as Constructive Interference in Steady State (CISS), Fast Imaging Employing Steady-state Acquisition (FIESTA), T2 Sampling Perfection with Application optimized Contrasts using different flip angle Evolution (SPACE), 3DT2, etc. (Figure 1). These sequences best delineate the morphology of the cisternal trigeminal nerve.^9,10 Additionally, the offending arteries or veins are seen as serpiginous flow voids that contact or compress the trigeminal nerve. Compressed nerves can be displaced, deformed, or appear atrophic. Nerve displacement or atrophy directly represent clinically significant compression and have been reported as 97% specific for classical TN. Moreover, compression of the trigeminal nerve at its entry into the brainstem has a nearly 100% sensitivity and positive predictive value.^6,9–11 Although heavily T2-weighted sequences yield excellent anatomic detail, there is often poor contrast between the nerves and the vessels. There is utility in contrast-enhanced 3D-CISS imaging to improve the characterization of high-grade neurovascular compression, localize the side of patient symptoms and predict the outcome following microvascular decompression (MVD). In conjunction with high-resolution MRI, an MR angiogram allows for localization and identification of vertebrobasilar branches in the posterior fossa. There is some utility in post-contrast enhanced T1W imaging of the brain, which may improve visualization of neurovascular relationships by causing the vessels to enhance. Furthermore, a post-contrast T1-weighted sequence helps rule out non-neurovascular abnormalities, such as enhancing masses in the cerebellopontine angle, skull base, leptomeninges or cranial nerves, as well as perineural spread of tumor. The diffusion-weighted imaging (DWI) sequence can distinguish lesions such as an epidermoid which demonstrates diffusion restriction. ¹¹ The FLAIR sequence may help suggest multiple sclerosis which is a cause of secondary TN.^12,13

Figure 1.

81-year-old female with long-standing sharp right face pain. Coronal high-resolution T2WI MRI (a) shows abutment of the right trigeminal nerve by a branch of the right superior cerebellar artery (red arrow). Axial high-resolution T2WI MRI (b) shows resultant volume loss of the nerve (yellow arrow); note normal bulk on the left (green arrow).

Management

The most common first-line management is pharmacologic therapy. ¹⁴ Transcutaneous approach (nerve stimulation, focused ultrasound, transcranial MR cortical stimulation), percutaneous (chemodenervation with alcohol or glycerol, radiofrequency ablation, cryoablation, nerve block, balloon compression), radiotherapy (CyberKnife, Gamma Knife) and open surgical options such as MVD are available if conservative therapy fails.^14,15

Glossopharyngeal neuralgia

Glossopharyngeal neuralgia (previously termed “vagoglossopharyngeal neuralgia”) is described by a pattern of unilateral, brief (lasting few seconds to 2 min), sharp stabbing pain with sudden onset and termination in the distributions of both the glossopharyngeal nerve, and the auricular and pharyngeal branches of the vagus nerve. ³ Pain is typically experienced in the ear, base of tongue, pharynx, and tonsillar fossa and precipitated by coughing, chewing, or swallowing.^3,16,17 Rarely it has also been associated with hemodynamic instability including cardiac syncope due to activation of vagal reflex pathways likely within the dorsal motor nucleus of the vagus nerve.^18,19 The nerve at its emergence from the brainstem is at risk of compression by an enlarged posterior inferior cerebellar, vertebral, or anterior inferior cerebellar artery. Non-vascular etiologies include tumors, multiple sclerosis, Chiari I morphology, infarct, neck trauma, or elongated styloid process (Eagle syndrome).^3,20–22 Occasionally, GN can also be caused by compression as a post-operative complication of trigeminal nerve MVD. ²³ When compared to TN, GN is less common, likely due to the short length of central myelin along the glossopharyngeal nerve that offers only a small anatomical area for clinically significant neurovascular compression. ²⁴

Imaging

CT of the head is inadequate to visualize the glossopharyngeal nerve, but it is useful to evaluate the pars nervosa of the jugular foramen that houses the glossopharyngeal nerve. ²⁵ As in TN, evaluation of GN is also best performed with MRI with high resolution T2-weighting imaging such as CISS, FIESTA, T2-SPACE, and with vascular imaging such as MR angiography with time-of-flight.^22,24 The extent of vascular compression can be analyzed by the absence of CSF between nerve and the offending vessel, as well as by structural change causing concavity due to vascular compression (Figure 2). ⁷ Of note, evaluation of the supraolivary fossette which is the medial-most portion of the CPA and is in close proximity to the root entry zone (REZ) is an important component of pre-surgical workup. ²⁶ The primary objective of imaging is to exclude non-vascular causes as mentioned previously. Using contrast-enhanced MRI to evaluate mass lesions and multiple sclerosis, along with FLAIR and diffusion sequences, is crucial in this exclusion process.

Figure 2.

60-year-old female with intermittent stabbing left throat pain. Axial T2-SPACE image through the brainstem demonstrates the V4 segment of the left vertebral artery (red arrow) contacting the left IX/X nerve complex (yellow arrow) near the root entry zone. Note the normal right side (green arrow).

Management

First-line treatments include pharmacologic therapy with anticonvulsants. In patients not responding to medical therapy or those complicated by adverse reactions, interventions such as MVD, stereotactic radiosurgery, peripheral glycerol rhizotomy, CT-guided percutaneous tractotomy–nucleotomy, and percutaneous thermorhizotomy have been reported as options.^27–32

Vestibulocochlear nerve compression

Vascular compression of the vestibulocochlear nerve and its clinical significance remain controversial. The most thought vascular offender is the anterior inferior cerebellar artery loops. However, Clift and colleagues did not find a significant correlation between symptoms and vascular compression of the vestibulocochlear nerve. ³³ Other theories such as advancing age and arterial elongation, pulsatile vascular compression causing demyelination, and atherosclerotic hardening of the arterial wall have also been reported. Imaging techniques are similar to that discussed with the trigeminal nerve, although, whether the presence of neurovascular conflict is related to symptomatology is debatable.

Occipital neuralgia

Occipital neuralgia is defined by unilateral or bilateral paroxysmal sharp pain in the distribution of the greater, lesser, and/or the third occipital nerve. ³ The pain may be associated with dysesthesia or allodynia of the scalp. ³ Most cases of occipital neuralgia are idiopathic. Other specific causes include trauma, prior skull base surgery, atlantoaxial osteoarthritis, or mass lesion.^34,35 Vascular compression is relatively rare, but the most common vascular offenders include an anomalous ectatic vertebral artery, ³⁶ fenestrated vertebral artery, ³⁷ and posterior inferior cerebellar artery. ³⁵ A critical differential to keep in mind is temporal arteritis which can present as occipital neuralgia even in the absence of an elevated erythrocyte sedimentation rate level as the management includes prompt administration of steroids. ³⁸

Imaging

The utility of imaging is limited to identifying the small proportion of cases that are not idiopathic. CT of the head and cervical spine can show post-traumatic or degenerative disease at the C1-C2 articulation. MRI of the brain and cervical spine with inclusion of T2-weighted sequences have been shown to depict the offending vessels. Furthermore, T2-weighted imaging and contrast enhanced imaging can help detect lesions causing occipital neuralgia.

Management

Conservative management with cervical collars, peripheral nerve stimulation, analgesics, antimigraine medication, local nerve block, and nerve ablation have been attempted, with variable degrees of success. ³⁴ Surgical treatments include greater occipital nerve decompression and C1-C2 arthrodesis.^39,40

Hemifacial spasm

Hemifacial spasm is characterized by painless, paroxysmal spasm of the orbicularis oculi muscle secondary to unilateral hyperexcitability of the facial nerve. This condition can often progress in frequency and severity to involve the remainder of the facial muscles and, rarely, the contralateral side. ⁴¹ Primary hemifacial spasms are typically the result of vascular compression of the nerve at the anterior caudal REZ by the ipsilateral posterior inferior cerebellar, anterior inferior cerebellar, vertebral, basilar, or cochlear artery.^42–45 Even gentle contact by a cerebellar artery on the centrally myelinated nerve fibers is sufficient to cause hemifacial spasm. ⁴³ Few cases of vascular compression of the distal, cisternal portion of the facial nerve have also been reported, identified in patients with recurrent hemifacial spasms or failed MVD procedures.^45,46,47

Imaging

CT of the head with contrast and CT angiography of the head can reveal ectasia, dolichoectasia, or malposition of the vertebrobasilar system, but neither can detect nerve compression.^48–50 Similarly, digital subtraction angiography (DSA) cannot depict the exact relationship between the vessels and nerves. ⁵¹ The best imaging tool is an MRI with high-resolution T2-weighted imaging or source MR angiography images that show serpentine asymmetric signal void representative of a compressive vessel at the facial nerve root exit zone in the medial CPA (Figure 3). ⁵¹ MRI FLAIR sequence is valuable in evaluating for underlying multiple sclerosis presenting as hemifacial spasm. ⁵² Post-contrast MRI sequences can also provide information on other secondary etiologies of hemifacial spasm such as perineural tumor spread and cranial neuritis. ⁵³

Figure 3.

55-year-old female with right facial hemispasm and twitching of the right lip. Axial high resolution T2WI MRI (a) and Sagittal T2WI MRI (b) show abutment of the right facial nerve (yellow arrow) by a vessel of unclear origin (red arrow).

Management

The two most accepted treatments for hemifacial spasms are botulinum toxin injection which provides sustained symptomatic relief by blocking acetylcholine release from presynaptic motor neurons and MVD which has a greater than 90% reported success rate in addressing the underling compressing vascular loop.^54,55

Trochlear nerve palsy

The most common etiology of unilateral trochlear nerve palsy is congenital. ⁵⁶ However, the thin morphological structure, the long intracranial course and the slender connection to the brainstem render the trochlear nerve highly susceptible to trauma and neurovascular compression.^57–59 Indeed, up to 75% of cases of bilateral trochlear nerve palsy have been reported to be a result of trauma. ⁵⁶ Patients may present with vertical diplopia, ipsilateral hypertropia without ptosis, and head tilt to the contralateral side. ⁶⁰ Etiologies include neurovascular compression due to internal carotid artery compression, aneurysms, and subarachnoid hemorrhage.^58,61

Imaging

The cisternal segment of the trochlear nerve is difficult to identify reliably on conventional MRI. As in TN, the utilization of high-resolution 3D sequences such as FIESTA have been shown to identify the trochlear nerve (Figure 4). ⁶² Additionally, using a voxel size smaller than the diameter of the trochlear nerve enables better visualization of the nerve. ⁶² Another study demonstrated easier identification of the trochlear nerve by using anatomic landmarks such as the trochlear groove and the trochlear cistern on fluid sensitive sequences. ⁶³

Figure 4.

58-year-old female with vertical diplopia and left trochlear nerve palsy. Coronal T2WI MRI (a) shows slight prominence of the left superior cavernous sinus at the expected location of the trochlear nerve (green arrow). Coronal T1 post-contrast image (b) shows ectasia of the left internal carotid artery (red arrow), presumed to be abutting the trochlear nerve (yellow arrow).

Management

Treatment of the underlying neurovascular cause, particularly in cases of ICA aneurysms or subarachnoid hemorrhage due to ruptured posterior communicating artery aneurysms.^58,61

Abducens nerve palsy

Isolated abducens nerve palsy is rare and often results from neurovascular compression of the abducens nerve at the REZ by dolichoectasia or aneurysms in the vertebrobasilar system.^64–67 Specifically, the most common offending vessels include the basilar artery, vertebral artery, and anterior inferior cerebellar artery. ⁶⁸ Other etiologies of isolated nerve palsy include meningitis, malignancy, uncontrolled diabetes mellitus or hypertension, petrous apex or orbital syndromes, cavernous sinus syndrome, pontine infarct involving the abducens nerve fascicle, intracranial hypertension or hypotension.^69,70 Furthermore, the etiology is not definitively identified in about 18–30% of patients. ⁷¹

Imaging

CT of the head with contrast and CT angiography of the head can demonstrate distinct dolichoectasia of the vertebrobasilar system but as in the previously described neurovascular compression syndromes, neither imaging modality can detect nerve compression. However, the bone reconstructions in a CT brain is valuable for assessing the skull base and bony foramina, thereby ruling out alternative causes of abducens nerve palsy pertaining to the course of the cranial nerve from the brainstem to the orbit. Additionally, CT angiography of the head is beneficial in diagnosing occult carotid-cavernous fistulas, which can result in abducens nerve palsy. ⁷¹ The gold standard for visualization of the nerve includes an MRI of the brain with thin section high resolution T2-weighted imaging and enhanced T1 imaging or source MR angiography images, as these techniques delineate cranial nerves surrounded by CSF, with high spatial resolution (Figure 5).^68,73

Figure 5.

75-year-old female with diplopia and right VI nerve palsy. Axial high-resolution T2WI shows dolichoectasia of the basilar artery (red arrow), coursing along the exit point at the level of right VI cranial nerve. Note the normal left VI cranial nerve (yellow arrow).

Management

Various treatments have been reported including observation, prism lenses, and MVD. Interestingly, MVD for the management of trigeminal neuralgia has been reported to cause temporary abducent nerve neurapraxia due to manipulation of the dolichoectatic vessels and stretching of the abducens nerve, for which observation is only required. ⁷⁴ However, due to the small number of surgically treated cases of isolated abducens nerve palsy, determining surgical indication and timing of MVD has been challenging. ⁶⁸ Spontaneous recovery due to neurovascular compromise is presumably low and therefore treatment with MVD is a strong consideration in long-standing abducens nerve palsy (4–6 months or longer). ⁶⁸

Medullary compression

Vascular indentation and mass effect on the medulla can result in medullary compression syndromes that presents with ataxia, vertigo, persistent headaches, limb weakness, dysarthria, and dysphagia. ⁷⁵ The most common site of compression is the anterolateral aspect of the medulla and the most common offending vessels are the vertebral artery and the posterior inferior cerebellar artery. ⁷⁵ Medullary compression is more common in the older population with hypertension and diabetes due to progressive vascular wall damage, ⁷⁶ although some studies report equipoise among normotensive and hypertensive patients. ⁷⁷

Imaging

CT angiogram of the head demonstrates dolichoectasia of the vertebrobasilar system, but medullary compression cannot be appreciated on a CT angiogram study. The best imaging technique is an MRI of the brain with heavily weighted T2 sequences that depicts dolichoectasia of the vertebrobasilar system with compression, indentation, or deformity of the medulla (Figure 6). Pre-operative evaluation also includes 3D-gradient echo T2-weighted imaging (CISS) and MR angiography time-of-flight.^78–81 However, a major limitation of 3D sequences are the flow-related signal variability of vessels and CSF pulsation artifacts. ⁸²

Figure 6.

Schematic representation medullary indentation by dolichoectatic vertebral artery. (a) 62-year-old female with ataxia and vertigo. Axial T2WI MRI (b) shows indentation and deformity of the left lateral aspect of the medulla (green arrow) by a dolichoectatic vertebral artery (red arrow). (c) 35-year-old female with persistent throbbing headaches. Axial T2WI MRI (b) shows mass effect on the anterolateral left medulla by a dolichoectatic vertebral artery (red arrow).

Management

Conservative management with antiplatelets, anticoagulants, and analgesics has been reported to be effective. ⁷⁵ MVD of the medulla is not a standard procedure but has been reported to have significant improvement of deficits. However, some authors recommend consideration of MVD in selected patients with intractable severe hypertension, based on the lack of significant improvement and potential for complications from new cranial nerve lesions. ⁸³

Osseous etiologies

Cervical ribs

Cervical ribs (CR) are supernumerary ribs arising as an extension of the lateral process of C7 vertebra during development. It occurs in 0.5–1.0% of the population.^84,85 The prevalence of a CR is more common in women than men. ⁸⁶ The presence of a CR is about 25 times higher in patients with thoracic outlet syndrome (TOS). ⁸⁷ CR is classified into four types. Type 1 is a complete rib that articulates with the manubrium sternum and type 2 has a free distal tip that does not articulate with the sternum. Type 3 has a fibrous distal segment that is attached to the sternum and type 4 is just an extension from the transverse process of the C7 vertebra. Presence of a CR is found mostly incidentally; for a patient to be symptomatic with TOS, a combination of predisposing factors like a CR or fibrous bands along with aggravating factors including hyperextension/abduction of the upper limb are present. TOS can be neurogenic, vascular, or mixed. Ninety percent of the cases of TOS are neurogenic due to compression of the brachial plexus. This results in ipsilateral pain or paresthesia in the head, neck, shoulder, or arm. Prolonged compression can lead to atrophy of the intrinsic hand muscles and loss of function.^86,89 Vascular compression can be due to subclavian artery or vein involvement leading to thrombosis, as well as aneurysm formation and distal limb ischemia.

Imaging

Chest radiography or cervical radiography is the initial modality of choice to identify CR. Ultrasound in either B-mode or Doppler is also helpful in the setting of vascular TOS to identify the changes in vessel caliber and blood flow during adducted and abducted position of the arm.^90,91 In equivocal cases, a contrast-enhanced CTA or MRA can be helpful. CTA with 3D reconstruction is helpful in delineating the location and extent with adjacent anatomical structures in addition to identifying vascular compression and thrombosis. However, the application of provocative maneuvers with hyperabduction of the upper limb can be limited due to the gantry size.^92–94 Cervical ribs can often be misdiagnosed as an elongated transverse process. A coronal reconstructed image in CT will help differentiate between the two based on the articulation between the CR and vertebral body (Figure 7). ⁸⁶ MRA with T1W sagittal sequences can better demonstrate neurovascular compression along with vascular thrombosis, whereas coronal sequences aid in assessing the brachial plexus. Images can be acquired pre- and post-provocative maneuvers with arm adduction and abduction while keeping the head and neck in neutral position.^92,95 An additional benefit of MRI in multiple positions is the lack of radiation.

Figure 7.

54-year-old male with intermittent left Horner syndrome and left brachial plexopathy. Coronal CT neck image in the bone window (a) shows bilateral cervical ribs (yellow arrow pointing to the left). Sagittal image in the soft tissue window (b) shows the expected location of the left inferior cervical ganglion and brachial plexus (yellow circle), presumably compressed/stretched by the left cervical rib upon movement.

Management

For patients with persistent symptoms, management includes CR resection. ⁹⁶ Combined first rib resection along with CR resection will provide more space for the neurovascular bundle and thereby lower chance of symptom recurrence. ⁹⁶ For patients with incidentally discovered CR, counselling should be provided about the occurrence of TOS.

Bow hunter syndrome

Bow hunter syndrome or rotational vertebral artery occlusion syndrome is caused by vertebrobasilar insufficiency due to a rotational compression of the dominant vertebral artery. The second part of the vertebral artery runs vertically through the transverse foramina, typically of C1 to C6 vertebrae. Compression can be caused primarily by adjacent osteophytes, fibrous bands, herniated disc, tumors or secondarily due to post-intervention or trauma.^97–99 Aggravating factors include hypoplasia or stenosis of the contralateral vertebral artery. ¹⁰⁰ Depending on the level of posterior circulation insufficiency, symptoms can either be transient or persistent, varying from presyncope or syncope to strokes.

Imaging

Due to the wide range of nonspecific symptoms patients present with, an initial work up to exclude other possible causes including carotid occlusion and vestibular diseases is recommended. CT head can reveal offending agents such as osteophytes and ossification of the posterior atlantooccipital membrane. As per angiographic evidence, the most common sites of compression are typically at C1-C2 and C5-C7, which are the most dynamic parts of the artery.^101,101 Dynamic digital subtraction vertebral angiography remains the gold standard for diagnosis. Acquisition of images during the neutral position aids in assessing the patency of the artery, whereas images on rotated position of the neck will reveal the presence and level of stenosis (Figures 8 and 9).^102,103

Figure 8.

68-year-old male with rotational syncope. Axial CTA of the neck shows symmetric vertebral arteries (green arrows) in the neutral position (a) and asymmetric severe narrowing of left vertebral artery (red arrow) when head is rotated to the right (b).

Figure 9.

68-year-old male with rotational syncope (same patient as Figure 8). Conventional angiogram demonstrates normal filling of the left vertebral artery in the neutral position (a) and confirms severe narrowing when the head is rotated towards the right (red arrow, b).

Management

In patients with single patent vertebral artery with persistent symptoms and concern for impending stroke, management includes either open surgical intervention for vertebral artery decompression, vertebral fusion or minimally invasive endovascular methods involving coil embolization, and angioplasty with stenting. On the other hand, in patients with less severe and transient symptoms an individualized approach based on the etiology is recommended. Patients who opt for non-surgical management can be treated conservatively by antiplatelet therapy.^102,104

Golfer’s stroke

Golfer’s stroke is characterized by recurrent cerebral infarctions secondary to craniocervical artery dissection associated with playing golf. ¹⁰⁵ The repetitive rapid body and neck movement may result in torsional forces on the extracranial cervical arteries with each swing. ¹⁰⁶ Specifically, various studies have discovered that the V3 segment of the vertebral artery is exposed without the support of bony structures and rotates freely during inadvertent head movement, rendering it the most susceptible during golf swing movements.^107,108 In addition to dissection from mechanical shear, the extracranial vessels can get compressed by an elongated hyoid process, styloid process, or fibrous bands from the longus colli muscle.^109–111

Imaging

Doppler ultrasound can demonstrate the location of arterial dissection, with the added advantage of being able to reproduce the compression by the hyoid bone in the rotated neck position. Doppler velocities may appear normal in the neutral position but decreased significantly with neck rotation, as in a golf swing.^111,112 CT angiography of the neck in the neutral position can demonstrate close contact of the hyoid bone (usually greater horn) with the extracranial vasculature (Figure 10). CT angiography with the neck in a rotated position can demonstrate compression of the vasculature against the hyoid. ¹¹¹ MRI of the brain demonstrates an embolic pattern of strokes with infarcts in the anterior or posterior circulation, particularly on the diffusion weighted images. ¹¹¹ MR angiography can demonstrate intimal flaps within the dissected extracranial vessel or signal loss in the vessel related to compression. ¹¹¹

Figure 10.

A 57-year-old male (golfer) with multiple episodes of hemiparesis, tingling sensation and numbness in his left hand and face while playing golf. Axial CT angiogram of the neck (bone window) (a) and sagittal CT soft tissue of the neck (b) show compression of the right internal carotid artery (red arrow) by the right hyoid tubercle (yellow arrow and yellow circle).

Management

In addition to conservative management with antithrombotics,^113,114 definitive treatment is resection of identified osseous offenders such an elongated styloid, enlarged greater horn of hyoid, osteophytic spurs, or decompression of fibrous bands.^115,116 Other more invasive treatments include hemilaminectomy at the C1 level and C1-C2 posterior fusion.^101,117

Eagle syndrome

This condition is characterized by pharyngeal pain, painful deglutition, referred otalgia, facial paresthesia, and symptoms of arterial compression secondary to elongation of the styloid process.^118,119 Medial or lateral deviation of an elongated styloid process can compress the internal carotid artery or external carotid artery. ¹¹⁸ Symptoms may be either due to physical compression and reduced caliber of the affected vessel and/or irritation of the sympathetic nerve supply of the vascular wall. ¹¹⁸ Clinically, patients may present with local pain and tenderness (carotidynia) and pain in the distribution of the affected vessel. To elaborate, if the internal carotid artery is affected, then the patient may present with parietal headaches and pain in the distribution of the ophthalmic artery, without significant involvement caudal to the level of the eye. However, if the external carotid artery is involved, then the pain is usually referred to below the eye in the region supplied by various external carotid artery branches. ¹¹⁸ Furthermore, multiple recent reports of Eagle syndrome causing internal jugular venous stenosis have also been reported. ¹²⁰ Specifically, the upper-third segment of the internal jugular vein is thought to be most susceptible to compression due to adjacent bony structures such as the styloid process and transverse process of C1. ¹²⁰ Patients with venous compression present mainly with insomnia, hearing impairment, visual impairment and tinnitus. ¹²⁰ Diagnosis of Eagle syndrome is made by both physical examination and imaging. Palpation of the elongated ossified styloid process in the tonsillar fossa should elicit and exacerbate the characteristic symptoms.^118,121

Imaging

A panoramic radiograph may be used to determine if the styloid process is truly elongated. A length of 3 cm or longer in an adult is considered elongated (normal <2.5 cm). ¹²¹ In the absence of a panoramic radiograph, anteroposterior and posterior views of the skull should be obtained. The anteroposterior view is helpful to ascertain the presence of medial or lateral deviation of the styloid process. ¹²¹ Similarly, a CT of the neck is highly useful to evaluate both osseous and vascular detail in multiple planes and provides complementary information as that in the radiographs. ¹²¹ Furthermore, studies utilizing three-dimensional CT, three-dimensional angiography with near-infrared spectroscopy, and more recently three-dimensional virtual imaging have been reported for the diagnosis of symptomatic Eagle syndrome.^122–124

Management

Although conservative management with analgesics, anticonvulsants, antidepressants have been tried, surgical treatment is the only effective treatment.^125–127 Specifically, transoral and transcervical approach for resection of the elongated styloid process have been reported.^125,126 Use of a piezoelectric cutting device to reduce the risk of transient marginal mandibular nerve injury with the transcervical approach has also been suggested. ¹²⁷

Miscellaneous

Optic neuropathy

Compressive optic neuropathy is characterized by mass effect on the anterior visual pathway and is an infrequent cause of visual impairments. ¹²⁸ Vascular compressions have been reported at the optic nerve and optic chiasm, ¹²⁸ while the most common offenders include the internal carotid artery, anterior cerebral artery, posterior communicating artery, and rarely the ophthalmic artery and recurrent artery of Heubner. ¹²⁸ Other lesions such as cerebral cavernous venous malformations (also called cavernous hemangiomas or cavernomas) affecting the anterior visual pathways, ¹²⁹ meningiomas compressing the optic nerve, ¹³⁰ and rarely an anterior clinoid mucocele causing compressive optic neuropathy have been reported. ¹³¹ Furthermore, progressive optic neuropathy caused by compression due to a prolapsing or herniated gyrus rectus has also been reported.^132,133 The gyrus rectus is located at the very middle in the anterior cranial fossa, in close vicinity of the intracranial segment of the optic nerve and anterior part of the chiasm.^132,133

Imaging

The ideal imaging modality is MRI of the brain, with heavily weighted T2 sequences showing the optic nerve in contact with the herniated or prolapsed gyrus rectus with distorted contour along the gyrus (Figure 11).^132,133 In cases of neurovascular compression, the MRI can reveal indentation and mass effect of the optic chiasm or optic nerves by the culprit intracranial vessels. ¹³⁴ The compressed optic nerve or chiasm demonstrates T2 hyperintensity while the unaffected contralateral side may be normal in signal intensity and caliber. ¹³⁵

Figure 11.

51-year-old female with intermittent left eye visual obscurations and visual loss. Coronal high-resolution T2WI of the brain shows herniation of the left rectus gyrus (green arrow) on to the left optic nerve (yellow arrow).

Management

No definitive treatment exists for this rare condition. However, there are reports of MVD, anterior clinoidectomy, and optic canal unroofing that have shown benefit in this condition.^4,136 However, if the process is chronic, MVD may not result in adequate symptom control due to fibrosed or degenerative nature of the nerve. ¹³³ It is therefore imperative to identify these etiologies early to prevent permanent visual impairment.

Conclusion

High index of suspicion and optimal positioning for imaging is key in patients with compressive lesions of the head and neck. While a multimodality approach is critical in the evaluation of compressive lesions, an MRI utilizing high-resolution (heavily weighted) T2-weighted sequence is extremely useful as a starting point.

ORCID iDs

George K Vilanilam https://orcid.org/0000-0003-0845-670X

Erik H Middlebrooks https://orcid.org/0000-0002-4418-9605

Alok A Bhatt https://orcid.org/0000-0003-3400-7123