17 Rare Causes of Unilateral Peripheral Vestibulopathy

The vestibular system works like a push–pull pairing between each ear. There is an equal and opposite effect that is created with head movement that stimulates the vestibulo-ocular reflex (VOR). When this process is disturbed, eye movements are not coordinated, which can lead to the clinical finding of nystagmus and a patient complaint of vertigo. In essence, when there is an unequal and opposite coordination of the eye, the brain will think the head is moving when it is not.1 The fast phase of the nystagmus will move in the direction of the stronger (normal ear) signal. Another way to think of it is that the eyes will slowly drift toward the weak side and the normal side will create the fast-phase compensatory motion. Therefore, the fast phase of the nystagmus is usually in the direction of the normal ear.

Etiology

Vertigo symptoms with different disorders will vary in intensity and duration. A careful history is critical to develop a diagnosis. Commonly recognized causes of peripheral vertigo, such as Meniere’s disease, viral labyrinthitis/neuronitis, benign paroxysmal positional vertigo (BPPV), and perilymphatic fistula, are covered in other chapters. In this chapter, we discuss rare causes of peripheral vestibulopathy, including bacterial, traumatic, iatrogenic, and neoplastic causes. Presenting signs and symptoms, as well as clinical findings, are reviewed. Finally, work-up and treatment are covered. Ototoxicity is the usual cause of bilateral vestibulopathy, and that is covered at the end of the chapter.

Types and Treatment of Peripheral Vestibulopathy due to Rare Causes

Bacterial Infections

Infectious etiologies of peripheral vestibulopathy are usually viral in origin. The usual viruses considered are cytomegalovirus (CMV), mumps (i.e., paramyxovirus), and rubella (i.e., togavirus). Although rare, labyrinthitis can be caused by bacterial sources. Bacteria can enter the inner ear and cause a suppurative labyrinthitis, leading to vestibular damage. The bacteria can reach the inner ear through the round window, a fistula created by a neoplasm, or via the cerebrospinal fluid (CSF) space, internal auditory canal (IAC), or cochlear/vestibular aqueduct, as they do in meningitis. Neoplasms include cholesteatoma, glomus tumors, and metastatic disease. Histopathology usually shows an acute inflammatory response of neutrophils that eventually leads to destruction of the membranous labyrinth. Eventually, there is macrophage infiltration leading to formation of a granuloma and permanent scarring.^2,3 This may eventually lead to osteoblast formation and subsequent bone formation, as we see in meningitis. Obviously, the damage causes hearing loss, as well as a peripheral vestibulopathy. In the case of meningitis, the symptoms could be bilateral.

Another bacterial cause of vertigo is Lyme disease, which should be considered if the patient lives in an endemic area or has a history of a visit to such an area. Appropriate antibiotic therapy, such as doxycycline, should be used. Serum titers are followed for recovery.4

Tertiary syphilis can lead to a lymphocytic infiltrate of the temporal bone that can be damaging to the membranous labyrinth, leading to the formation of endolymphatic hydrops. In fact, presenting symptoms can be very similar to Meniere’s disease.⁵ Diagnosis requires a suspicion as well as a history of syphilis. The tertiary infection may develop years after the initial primary infection. Tertiary syphilis reaches its peak in the fifth or sixth decade of life.⁶ There may be an associated fluctuating hearing loss. Clinically, there may be a finding of Tullio phenomenon secondary to the intralabyrinthine scarring.⁷ A rapid plasma reagin (RPR) test and a fluorescent treponemal antibody test are usually positive. The sensitivity of the fluorescent treponemal antibody absorbed (FTA-ABS) is usually higher for tertiary syphilis. Ultimately, a cerebrospinal fluid Venereal Disease Research Laboratory (VDRL) test will be positive. Spirochetes may also be seen under dark-field exam of the CSF.⁸ Treatment consists of crystalline penicillin G, 2 million to 4 million units IV every 4 hours for 10 days. Prednisone is added if not contraindicated.⁹

Trauma

The most common form of posttraumatic vertigo is BPPV. Also, endolymphatic hydrops can occur as a result of trauma. (These topics are covered in other chapters.) A temporal bone fracture with or without associated hemorrhage can lead to direct injury or concussion to the inner ear or vestibular nerve itself. Meniere’s disease has also been seen to occur after trauma.^10,11 Other traumas without fracture, including airbag trauma, can induce vertigo.^11,12

As expected, there is a higher incidence of injury to the vestibular system with transverse fractures.^13,14 Typically, patients will have severe rotatory vertigo and may also have associated hearing loss. Testing should include electronystagmography (ENG), which will likely show reduced caloric function on that side. Expectant treatment with antivertigo medication, such as meclizine or lorazepam, and antinausea medication, such as promethazine or prochlorperazine, is the usual initial therapy.¹⁵ Usually the problem is self-limiting; however, vestibular rehabilitation may hasten recovery.¹⁶

Barotrauma refers to injury sustained from a failure to equalize the pressure of an air-containing space with that of the surrounding environment. The most common examples of barotrauma occur in air travel and scuba diving.^17,18 Barotrauma can also affect several different areas of the body, including the face and lungs. Barotrauma is caused by a difference in pressure between the external environment and the internal parts of the ear. Fluids do not compress under pressures experienced during diving or flying. Therefore, a fluid-containing space does not alter its volume under these pressure changes. However, the air-containing spaces of the ear do compress, resulting in damage to the ear if the pressure cannot be equalized.

Symptoms of barotrauma include fullness of the ear, ear pain, hearing loss, dizziness, tinnitus, and hemorrhage from the ear. The main concern with barotrauma is that the associated sensorineural hearing loss may be permanent. The other concern is that there is associated vertigo. This usually happens around the onset of the trauma. The vertigo is usually self-limiting but may be prolonged. Treatment can include decongestants; however, if there are signs of sudden hearing loss and vertigo, a course of steroids should be started.¹⁹

Perilymphatic fistula can also develop as a result of direct trauma or barotrauma. Leakage of perilymph can occur around the oval or round window. With severe blunt or penetrating trauma, there can be an obvious stapes dislocation leading to the fistula formation. The patient will complain of vertigo symptoms with head position change or Valsalva. Also, changes in pressure, such as in airplanes or elevators, can cause symptoms. Fistula testing can be conducted by pressurizing the canal with a pneumatic otoscope. Electronystagmography or electrocochleography testing may or may not show any positive findings.²⁰

Initially, conservative treatment is recommended if there is no associated hearing loss. This includes activity restriction, bed rest with head elevated, and laxatives. If there is associated hearing loss, it is recommended that exploration be done relatively quickly to maximize the potential for hearing return. Also, if conservative therapy for the vertigo symptoms fails, then exploratory surgery with packing off of the round and/or oval window may be indicated.^21,22,23

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