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|Year : 2015 | Volume
| Issue : 4 | Page : 636-637
VV Vaishnavathi1, Rajeswaran Rangasami1, Sudarshan Suresh2, Indrani Suresh2
1 Department of Radiology, Sri Ramachandra University, Tamil Nadu, India
2 Department of Radiology, Mediscan Systems, Tamil Nadu, India
|Date of Web Publication||4-Aug-2015|
V V Vaishnavathi
Department of Radiology, Sri Ramachandra University, Porur, Chennai - 600 116, Tamil Nadu
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Vaishnavathi V V, Rangasami R, Suresh S, Suresh I. Fetal hemimegalencephaly. Neurol India 2015;63:636-7
A 21-year-old female patient with 25 weeks of gestation was referred for fetal magnetic resonance imaging (MRI) for the evaluation of unilateral ventriculomegaly with the right lateral ventricle measuring 11 mm on sonography [Figure 1]a and b. Fetal MRI using half-Fourier acquisition single-shot turbo spin echo sequence revealed an enlarged right cerebral hemisphere with diffuse hypointensity of the cerebral white matter as compared to the left side, suggesting advanced myelination [Figure 1]c-f. The cerebral convexity sulci were visualized on the right side suggesting a sulcal pattern corresponding to 27-28 weeks on that side. The sulcal pattern corresponded to 25 weeks on the left side [Figure 1]d and f. The lateral ventricles measured 11 mm on the right side and 6 mm on the left side. A radiological diagnosis of hemimegalencephaly was made that was confirmed on autopsy (the couple opted for termination of pregnancy). Though the exact cause of hemimegalencephaly (HME) is unknown, the main possibility includes a genetic mutation. These are of three types: (1) an isolated form; (2) a syndromic form occurring with developmental disorders or neurocutaneous syndromes; and, (3) total hemimegalencephaly.  Clinically, macrocephaly is the first sign at birth, the main symptoms being epilepsy intractable to medications, and the presence of focal neurological deficits. The MRI findings are enlarged cerebral hemisphere with an enlarged lateral ventricle with straight frontal horns pointing anteriorly and superiorly, and, an ipsilateral normal or dysplastic cerebral cortex. , There may be associated cortical thickening and cortical abnormalities like agyria, pachygyria or polymicrogyria.  Accelerated myelination in the white matter is diagnosed on MRI when one observes the white matter becoming hypointense on T2-weighted images (as seen in our case); or, hyperintense on T1-weighted images (T1/T2 shortening). 
|Figure 1: (a and b) Axial sonographic images showing a unilateral ventriculomegaly (arrow); (c and d) axial, (e and f) coronal T2 - weighted half - Fourier acquisition single - shot turbo spin echo magnetic resonance images showing mild ventriculomegaly on the right side (arrow) and an enlarged right cerebral hemisphere (open arrow). There is hypointensity of the right cerebral white matter (asterisk). Cerebral convexity sulci are visualized on the right side (curved arrow)|
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Whenever the antenatal sonography shows an enlarged lateral ventricle or cerebral hemisphere, a complementary fetal MRI is helpful to diagnose the condition and for counseling regarding the treatment modalities.  Hemispherectomy is the surgical treatment of choice for the intractable epilepsy from HME. 
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