Traumatic brain injury and vestibulo-ocular function: current challenges and future prospects

Figures & data

Figure 1 Representation of the ear from the outer ear (A) to the middle ear (B) to the inner ear (C).

Figure 2 Representation of the two divisions of the inner ear.

Note: The cochlea is the snail-shaped portion on the right, and the semicircular canals on the left represent the vestibular system.

Figure 3 Representation of the endolymph (pink), which is the fluid contained in the membranous labyrinth of the inner ear and has a higher level of potassium than sodium.

Figure 4 Representation of the three semicircular canals that detect angular head accelerations and the two otolith organs (utricle and saccule) that detect linear head accelerations.

Note: Adapted with permission from Benign Paroxysmal Positional Vertigo [webpage]. Copyright © 2016, Timothy C. Hain, MD. [Updated Dec 27 2006]. Available from http://www.dizziness-and-balance.com/images/master-ear.jpg.

Figure 5 The bottom image represents orientation of hair cells within the utricle when the head is upright.

Notes: The hair cells are surrounded by a gelatinous substance and hold the microscopic otoconia. The image on the right represents the response with pitching the head forward, which results in a deflection of the hair cells due to a gravitational pull.

Figure 6 Representation of dislodged otoconia in both the posterior and horizontal canal.

Note: Adapted with permission from Benign Paroxysmal Positional Vertigo [webpage]. Copyright © 2016, Timothy C. Hain, MD. [Updated Dec 27 2006]. Available from http://www.dizziness-and-balance.com/images/master-ear.jpg.

Figure 7 Representation of the endolymphatic flow.

Notes: (A) Orientation of the cupula when the head is upright and stationary. (B) Head movement in one direction, resulting in endolymphatic flow in the opposite direction and toward the cupula (ampullopetal). Ampullopetal flow causes deflection of the cupula toward the utricle (utriculopetal). (C) Head movement that results in endolymph moving away from the amupulla (ampullofugal), causing deflection of the cupula away from the utricle (utriculofugal).

Table 1 Represents the excitatory and inhibitory connections of each SCC with the muscles of both eyes, which results in specific compensatory responses between the vestibular system and eye muscles

Semicircular canal (SCC)	Excitation	Inhibition
Posterior	Ipsilateral superior oblique Contralateral inferior rectus	Ipsilateral inferior oblique Contralateral superior rectus
Anterior	Ipsilateral superior rectus Contralateral inferior oblique	Ipsilateral inferior rectus Contralateral superior oblique
Horizontal	Ipsilateral medial rectus Contralateral lateral rectus	Contralateral medial rectus Ipsilateral lateral rectus

Table 2 Ewald’s three laws, which govern vestibular diagnostic testing

1	Stimulation of a semicircular canal (SCC) generates eye movements in the plane of that canal.
2	In the horizontal canals, movement of the endolymph toward the ampulla (ampullopetal) causes deflection of the cupula toward the utricle (utriculopetal) and results in a greater neural activity (excitation) compared to movement away from the utricle (utriculofugal).
3	In the vertical canals (anterior and posterior), movement of the endolymph away from the ampulla (ampullofugal) causes greater deflection of the cupula away from the utricle (utriculofugal) and results in a greater excitation compared to utriculopetal movement, which is opposite to that in the horizontal canals.

Note: Ewald’s Law 1 is specific to compensatory eye movements to head movements as well as the foundation for identifying canal involvement in benign paroxysmal positional vertigo.

Table 3 Summary of vestibular disorders associated with head trauma and corresponding clinical presentation (adapted from Ernst).¹⁰

Vestibular disorder	Duration of vertigo	Exacerbating factors	Diagnostic tests	Treatment
BPPV	<1 minute	Position changes	Dix-Hallpike (super/posterior scc) or Roll Test (horizontal scc) – clinical and/or with video goggles/frenzel lenses	Canal specific repositioning maneuvers
Central Vertigo	Varies	Non-specific/more constant	Neuro exam; Imaging	Pharmaceutical management; Habituation; Physical therapy
Delayed Endolymphatic Hydrops/Meniere’s Disease	Minutes to Hours	Intermittent spells – possibly related to diet, allergies, other illnesses, stress, hormonal changes, migraines and/or barometric pressure changes	Comprhensive audiogram; Electrocochleography (ECoG) and Vestibular Evoked Myogenic Potentials (VEMP)	Lifestyle changes and/or pharmaceutical management most conservative; Intratympanic Gentamicin (ITG); Vestibular nerve section (most invasive)
Labyrinthine Concussion	Hours to Days	Movement-related dizziness and/or unsteadiness; Possibly position changes	Comprehensive audiogram; Videonystagmography (VNG); Computerized Vestibular Ocular Reflex (VOR) testing	Acute: pharmaceuticalmanagement (eg, anti-emetic, steroids); Chronic: vestibular therapy
Perilymphatic Fistula/Superior Canal Dehiscence (SCD)	Minutes to Hours; may not be present	Similar to hydrops; pressure changes; loud sounds	Comprehensive audiogram with VEMP and High Resolution CT scan (temporal)	Conservative per patient education to avoid straining and loud noises; Pharmaceutical as noted with hydrops; Surgical repair (“patching”)

Note: Adapted from Ernst A, Basta D, Seidl RO, Todt I, Scherer H, Clarke A. Otolaryngol Head Neck Surg. 2(4):554–558. Copyright © 2005 by Sage Publications, Inc. Reprinted by Permission of SAGE Publications, Inc.¹⁰

Abbreviations: BPPV, benign paroxysmal positional vertigo; SCC, semicircular canal; CT, computed tomography.

ErnstABastaDSeidlROTodtISchererHClarkeAManagement of posttraumatic vertigoOtolaryngol Head Neck Surg200524554558

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