• 10 SECTION Nystagmus

Peripheral Vestibular Nystagmus

Key Facts

•Unidirectional horizontal–torsional jerk nystagmus with fast phase directed away from side of vestibular lesion

•Nystagmus resolves within days (brainstem compensation)

•Common causes:

•viral labyrinthitis

•viral neuronitis

•benign paroxysmal positional vertigo (BPPV)

•Ménière disease

•otic trauma

•middle or inner ear infections, tumors, or stroke

•autoimmune conditions

•perilymphatic fistula

Clinical Findings

•Nystagmus fast phase is always directed to same side regardless of gaze position, unlike sidebeat nystagmus, in which the fast phase is directed to the side of gaze (direction-changing)

•Nystagmus amplitude increased by ocular occlusion or strong plus (Frenzel) lenses (unlike sidebeat nystagmus)

•Saccades, pursuit are normal (unlike sidebeat nystagmus)

•Patient often complains of nausea, vomiting, vertigo, hearing loss and/or tinnitus and falls to the side of the lesion

•Patient often has severe imbalance but no extremity or speech ataxia

•Manifestations induced or exacerbated by rapid shifts in head position

Ancillary Testing

•Otologic, audiologic, and vestibular testing (including videonystagmography) helps confirm diagnosis

•Brain imaging, which is usually not necessary if diagnostic criteria are met, will be normal unless there are structural abnormalities in middle or inner ear

Differential Diagnosis

• Sidebeat nystagmus

Treatment

•Oral antihistamine and antiemetic are helpful palliatives for vertigo and nausea

•Direct other treatment at underlying lesion

•In BPPV, otoconial repositioning maneuvers may be indicated

Prognosis

•Nystagmus resolves within days

•In BPPV, otoconial repositioning maneuvers may be curative

•Other symptoms of viral labyrinthitis and neuronitis resolve spontaneously within weeks

• 10 SECTION Nystagmus

Acquired Binocular Pendular Nystagmus

Key Facts

•Acquired horizontal, vertical, torsional, elliptic, or circular pendular nystagmus

•Causes:

•multiple sclerosis

•other brainstem lesions

•congenital midline dysgenesis

•Whipple disease

Clinical Findings

•Horizontal, vertical, torsional, elliptic, or circular pendular nystagmus

•Patient usually complains of oscillopsia (smeary vision or illusion of fine movement of viewed objects)

•One eye may rise while the other falls (seesaw nystagmus)

•Eyes may move in synchrony with oscillations of palate, platysma, pharynx, larynx, or diaphragm (oculopalatal myoclonus)

•Eyes may converge synchronously with masticator muscle spasms (oculomasticatory myorhythmia)

Ancillary Testing

• MRI often shows pertinent lesions of brainstem

•Oculopalatal myoclonus: enlargement of inferior olive in medulla is sometimes visible on T2 sequences as a late finding

•Seesaw nystagmus: lesion is often in the diencephalic or midbrain region

•Oculomasticatory myorhythmia: serum and cerebrospinal fluid PCR is positive for Tropheryma whippelii DNA and small intestine biopsy shows characteristic pathology

Differential Diagnosis

•Congenital nystagmus

•Monocular pendular nystagmus of childhood

•Ocular flutter or opsoclonus

•Psychogenically induced eye movements

Treatment

•Medications that may help:

Seesaw nystagmus: baclofen, clonazepam

Oculopalatal myoclonus: clonazepam, scolopamine, valproic acid, gabapentin, or trihexyphenidyl

•But these medications only rarely reduce oscillopsia or improve vision and may exacerbate other neurologic manifestations

•Intramuscular and retrobulbar botulinum toxin injections do not reduce oscillopsia or improve vision

•Large extraocular muscle recessions do not reduce oscillopsia or improve vision

Prognosis

• Depends on underlying lesion

Fig. 10.9 Acquired binocular pendular nystagmus. Both eyes display a pendular nystagmus with an oval trajectory. The eyes look like egg beaters.

Fig. 10.10 Sagittal FLAIR MRI shows multiple high signal areas in the cerebrum and cerebellum, typical of multiple sclerosis.

Nystagmus Pendular Binocular Acquired