History of Present Illness
A 24-year-old female with a history of polysubstance (ethanol, marijuana, tobacco) abuse presented to the emergency room at another hospital with 2 months of worsening somnolence, confusion, and new hallucinations. She became progressively encephalopathic, requiring intubation for airway protection. There was noted persistence of symptoms prompting eventual transfer to our hospital, where ophthalmology was consulted for a diagnostic examination .
| OD | OS | |
|---|---|---|
| Visual acuity | Unable | Unable |
| Intraocular pressure (IOP) | 15 | 15 |
| Sclera/conjunctiva | White and quiet | White and quiet |
| Cornea | Clear | Clear |
| Anterior chamber (AC) | Deep and quiet | Deep and quiet |
| Iris | Unremarkable | Unremarkable |
| Lens | Clear | Clear |
| Anterior vitreous | Clear | Clear |
| Retina | Focal area of retinal whitening seen in by the inferior arcades ( Fig. 63.1A ) | Diffuse area of retinal whitening involving near the entirety of the inferior arcades associated with box-carring of the inferior arcade vessels ( Fig. 63.1B ) |
Questions to Ask the Family and Management Team at the Referring Hospital
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Did the patient report any eye or vision-related concerns before the neurologic decompensation? (Pain? Blurring? Scotomas?)
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Did the patient report any other major systemic symptoms before the neurologic decompensation? (Headache? Hearing loss?)
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Did the patient have a history of head trauma? Did the patient overdose with any substance just before experiencing the neurologic symptoms?
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Is there a family history of any similar problems?
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Has infection been ruled out as a possible etiology?
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What empiric treatment has been given to the patient already?
The relatives of the patient indicated that the patient had no reported changes in vision but developed migraines and reported episodic hearing loss the year prior, though hearing loss was never formally tested.
There was no history of trauma and no relevant family history of eye disease or vison loss.
The management team has ruled out infection. In terms of empiric treatment, the patient had been treated with intravenous acyclovir, multiple rounds of intravenous methylprednisolone, intravenous immunoglobulin (IVIG), and plasma exchange therapy with only temporary improvement in the neurologic status.
Assessment
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Bilateral branch retinal artery occlusions (BRAO), left eye greater than right eye (OS > OD) in the setting of white matter lesions (including the corpus callosum) on magnetic resonance imaging (MRI) and a history of episodic hearing loss
Differential Diagnosis
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Susac syndrome
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Multiple sclerosis
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Acute demyelinating encephalomyelitis (ADEM)
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Multifocal inflammatory leukoencephalopathy
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Hypercoagulable state
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Cannabis induced
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Less likely: Chronic traumatic encephalopathy, substance abuse
Working Diagnosis
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Susac syndrome
Testing
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In patients with the classic triad of Susac syndrome, including BRAOs, hearing loss, and encephalopathy such as the index patient, diagnosis is almost definite.
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Fluorescein angiography (FA) is extremely sensitive in detecting retinal vascular abnormalities, including arterial wall hyperfluorescence, Gass plaques (pseudoemboli composed of immune complex debris aggregates seen distant to bifurcation sites), and arterial collaterals. In Susac syndrome, there is a characteristic leakage of vessels distant from the site of ischemia.
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Perimetry should be done to document and assess visual field defects that may arise secondary to the BRAOs.
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MRI may show typical snowball white matter lesions, usually found at the corpus callosum; other lesions like deep gray matter involvement and leptomeningeal enhancement may also be seen (see Fig. 63.2 ).
