Neurology · Neuro-ophthalmology
The facts most likely to be tested
Peripheral vertigo presents with horizontal nystagmus that is suppressed by visual fixation and typically fatigues over time.
Central vertigo presents with purely vertical or torsional nystagmus that is not suppressed by visual fixation and does not fatigue.
Internuclear ophthalmoplegia (INO) is characterized by impaired adduction of the ipsilateral eye and abducting nystagmus of the contralateral eye, localizing to the medial longitudinal fasciculus (MLF).
Downbeat nystagmus is a classic sign of craniocervical junction pathology, such as a Chiari malformation.
Upbeat nystagmus is highly suggestive of lesions in the medulla or the anterior vermis of the cerebellum.
Pendular nystagmus, where the oscillations have equal velocity in both directions, is frequently associated with congenital vision loss or multiple sclerosis.
Opsoclonus-myoclonus syndrome is a paraneoplastic condition characterized by chaotic, multidirectional saccadic eye movements often associated with neuroblastoma in children.
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A 32-year-old woman presents with sudden onset of double vision and imbalance. Physical examination reveals impaired adduction of the right eye during leftward gaze, while the left eye exhibits horizontal nystagmus during abduction. The patient has a history of recurrent sensory disturbances and fatigue. Visual fixation does not suppress the ocular movements.
What is the most likely anatomical location of the lesion causing these findings?
Medial longitudinal fasciculus (MLF)
The patient exhibits classic signs of internuclear ophthalmoplegia (INO), which is caused by a lesion in the MLF, a common finding in multiple sclerosis.
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High yield triage
Etiology / Epidemiology
Peripheral causes involve vestibular labyrinth; central causes involve brainstem/cerebellum lesions.
Clinical Manifestations
Peripheral shows horizontal nystagmus with fatigability; central shows vertical nystagmus without fatigability.
Diagnosis
Dix-Hallpike maneuver is the gold standard for BPPV; MRI brain is required for suspected central pathology.
Treatment
Epley maneuver for BPPV; avoid driving during acute vertigo episodes.
Prognosis
BPPV is self-limiting but prone to recurrence; central causes carry high mortality risk.
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Epidemiology & Etiology
Peripheral nystagmus is most commonly caused by Benign Paroxysmal Positional Vertigo (BPPV) or Meniere's disease. Central nystagmus is a red flag for stroke, multiple sclerosis, or posterior fossa tumors. Distinguishing between these is the primary clinical objective.
Pertinent Anatomy
The vestibulo-ocular reflex (VOR) coordinates eye movement with head rotation. Peripheral lesions affect the semicircular canals or vestibulocochlear nerve (CN VIII). Central lesions involve the vestibular nuclei or cerebellum.
Pathophysiology
Nystagmus results from an imbalance in tonic vestibular input. Peripheral lesions cause a slow drift toward the lesion side with a fast corrective phase toward the healthy side. Central lesions disrupt the neural integrator in the brainstem, often resulting in pure vertical or torsional nystagmus that does not suppress with visual fixation.
Clinical Manifestations
Peripheral nystagmus is horizontal, suppressed by visual fixation, and exhibits fatigability upon repeated testing. Central nystagmus is often vertical, pendular, or direction-changing and is not suppressed by visual fixation. Red flags include ataxia, dysarthria, or diplopia, which mandate urgent neuroimaging.
Diagnosis
The Dix-Hallpike maneuver is the gold standard for diagnosing BPPV, characterized by geotropic nystagmus. MRI brain with contrast is the diagnostic test of choice for central vertigo. HINTS exam (Head Impulse, Nystagmus, Test of Skew) is highly sensitive for identifying stroke in the acute vestibular syndrome.
Treatment
BPPV is treated with canalith repositioning maneuvers, specifically the Epley maneuver. For acute vestibular neuritis, meclizine or benzodiazepines provide symptomatic relief. Avoid long-term use of vestibular suppressants as they delay vestibular compensation. Central causes require treatment of the underlying ischemia or neoplasm.
Prognosis
BPPV has a high recurrence rate of up to 50% within 5 years. Central nystagmus prognosis depends on the underlying etiology; failure to identify a central cause can lead to permanent neurological deficit or death.
Differential Diagnosis
BPPV: brief episodes triggered by head movement
Vestibular Neuritis: continuous vertigo without hearing loss
Meniere's Disease: episodic vertigo with fluctuating hearing loss and tinnitus
Vestibular Schwannoma: progressive hearing loss and imbalance
Brainstem Stroke: nystagmus associated with focal neurological deficits