A Visual Field Defect in a Patient With History of Seizures

Jonathan J. Go; Rod Foroozan, MD


October 09, 2018


A porencephalic cyst may communicate with the ventricular system or may be separated from the ventricular system by a thin tissue layer.[6] An occipital location, such as that seen in this patient, is more common than a frontal location but less common than a more central location.[7]

Porencephalic cysts have been categorized as congenital and acquired. Congenital causes include intrauterine viral infection or intrauterine vascular injury. Acquired causes include trauma, surgery, infection, ischemia,[5] idiopathic causes, and stressful life events.[8] Mutations in the COL4A1 gene have also been linked to porencephalic cysts.[1] This patient's cyst appeared to be either congenital or at least longstanding, based on her history of seizures at a young age.

Visual impairment due to a porencephalic cyst has been noted.[9,10,11,12,13] Homonymous hemianopia is the most common cause of visual field loss,[10,11,12] owing to the cyst's localization posterior to the optic tract. Porencephalic cysts can be overlooked due to their infrequency. In one case, visual loss from a porencephalic cyst was initially misdiagnosed as glaucoma.[9] Other clinical findings reported to occur with porencephalic cysts have included seizures, motor deficits,[14] rhinorrhea, otorrhea,[6] psychosis,[15] gyrate atrophy,[16] West syndrome,[17] hallucination,[10] strabismus, nystagmus,[12] large cup-to-disk ratio,[18] cognitive deficits, and microcephaly.[5]

MRI typically reveals a brain cyst with a well-defined border, with a white matter lining with or without gliosis. Low cerebrospinal fluid signal intensity is present on T1 sequences, high intensity is present on T2 sequences, intensity is suppressed on FLAIR sequences, and restricted diffusion is not present on diffusion-weighted MRI. The imaging findings from this patient's axial T1 post-contrast MRI scan are consistent with those reported previously.

Differential diagnoses of an intracranial cystic lesion include porencephalic cyst, arachnoid cyst, schizencephaly, and ependymal cyst.[8] The distinguishing features[5,8] of these conditions are listed in the Table.

Table. Characteristics of Intracranial Cystic Lesions

Differential diagnosis Distinguishing features
Arachnoid cyst Extra-axial
Displaces brain away from skull
Schizencephaly Heterotopic grey matter
Extends from ventricle to brain surface
Ependymal cyst Intraventricular
Porencephalic cyst Interaxial
No displacement away from skull
Gliotic or spongiotic white matter
Variable length
May involve ventricles
Often symptomatic

Treatment of porencephalic cysts has included antiepileptic medication, such as valproate,[17] and surgical intervention.[19] Because this patient's symptoms were limited to a nonprogressive visual field defect, no treatment was suggested other than monitoring of visual function.

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