Disorders• 8 SECTIONMotor Ocular Brainstem

Paramedian Pontine Syndrome

Key Facts

•Impaired ipsilateral horizontal gaze and impaired adduction of ipsilateral eye (one and a half syndrome)

•May have ipsilateral gaze deviation (see Acute horizontal gaze deviation)

•Intact vertical gaze

•Common causes:

•stroke

•demyelination

•tumor

•vascular malformation

•myelinolysis

Clinical Findings

•Impaired ipsilateral horizontal gaze and impaired adduction of ipsilateral eye (one and a half syndrome)

•Intact vertical gaze

•Associated findings:

•exotropia with contralateral eye deviated outward (pontine exotropia)

•vertical misalignment (skew deviation)

•nystagmus

•saccadic pursuit

•Pupils are normal

•Doll’s head maneuver fails to elicit normal eye movements

Ancillary Testing

•MRI detects tumor, myelinolysis, and vascular malformation, but only sometimes detects stroke and multiple sclerosis

Differential Diagnosis

•Myasthenia gravis

•Fisher syndrome

•Wernicke encephalopathy

•Frontoparietal infarct

Treatment

•Stroke: supportive care

•Tumor: search for primary site, lumbar puncture

•Vascular malformation: radiation or surgery, as appropriate

•Multiple sclerosis: immunomodulatory agents

•Fisher syndrome: plasmapheresis or intravenous immunoglobulin

•Wernicke encephalopathy: thiamine

Fig. 8.10 Right paramedian pontine syndrome. The eyes display a left exotropia in primary position. In right gaze, neither eye crosses the midline. In left gaze, the right eye does not cross the midline and the left eye has a normal excursion. This pattern is called a one and a half syndrome, one of the manifestations of paramedian pontine dysfunction.

A B

Fig. 8.11 Cavernous hemangioma of the left pons. (A) Axial FLAIR MRI shows a round mass (arrow) in the left paramedian pons with inhomogenous signal.

(B) After surgical extirpation, the mass (arrow) is much smaller.

Syndrome Pontine Paramedian

Disorders• 8 SECTIONMotor Ocular Brainstem

Dorsolateral Medullary (Wallenberg) Syndrome

Key Facts

•Acute onset vertical diplopia, oscillopsia, ipsilateral ptosis and miosis (Horner syndrome), imbalance, severe nausea and vomiting, hoarseness, and swallowing difficulty

•Caused by infarction in domain of posterior inferior cerebellar artery from arteriosclerosis or dissection in vertebral artery

•MRI shows infarction in dorsolateral medulla and sometimes inferolateral cerebellar hemisphere

•Intensive care monitoring necessary because of early risk of aspiration

•Full recovery common but takes months

Clinical Findings

•Hypertropia (skew deviation), ipsilateral ptosis and miosis (Horner syndrome), torsional nystagmus

•Under closed lids, eyes deviate horizontally to side of lesion, saccades toward side of lesion are hypermetric, and saccades away from lesion are hypometric (ocular lateropulsion)

•Non-ophthalmic findings:

•ataxia

•nausea and vomiting

•hoarseness and swallowing difficulty

•ipsilateral trigeminal hypesthesia

•contralateral extremity hypesthesia

Ancillary Testing

•MRI shows restricted diffusion in dorsolateral medulla and sometimes inferolateral cerebellar hemisphere within first week

•May also show blood in vertebral artery wall if there has been a dissection

•Magnetic resonance angiography may show narrowing or occlusion of ipsilateral vertebral artery

Differential Diagnosis

•Cerebellar hemorrhage or tumor

•Multiple sclerosis

Treatment

•Needs intensive monitoring within first 48 h because of risk of aspiration

•Consider short-term anticoagulation if vertebral dissection is proven by imaging

•Palliative care for vertigo, intractable vomiting and hiccupping, swallowing difficulty

•Physical therapy for ataxia

•Occlusion, prism for diplopia of skew deviation

Prognosis

• Recovery is prolonged and some deficits may persist

Fig. 8.12 Right dorsolateral medullary (Wallenberg) syndrome. There is mild right upper lid ptosis and miosis (Horner syndrome). The left eye is higher than the right eye (left hypertropia; see Skew deviation). In left gaze, the eyes display a clockwise rotary jerk nystagmus.

A B

Fig. 8.13 (A) Axial T2 MRI shows high signal in the right dorsolateral medulla (arrow) and inferomedial cerebellar hemisphere (arrowheads), indicating infarction in the territory supplied by the posterior inferior cerebellar artery. (B) MRA shows absence of signal in expected location of right vertebral artery which has been occluded by dissection (arrowheads).

Syndrome (Wallenberg) Medullary Dorsolateral