|
|
| Images
below require Macromedia's Flash Player to view |
 |
Neuroradiology Case of
the Week
Case 196
Thomas Hughes, MD and Per-Lennart Westesson, MD, PhD, DDS
Clinical
Presentation:
Patient is a
2-year-old
female with seizures.
Radiological Findings: There is periventricular subependymal heterotopic gray matter present bilaterally (arrows). Also seen are various dysmorphic features, including agenesis of the corpus callosum, dysmorphic ventricles, and a right parietal porencephalic cyst. Identified on the CT image only are stable postsurgical changes following correction of craniosynostosis.
|
|
| Figure 1. T1WI |
Figure 2. T2WI |
|
|
| Figure 3. T1WI + C |
Figure 4. CT |
Diagnosis: Subependymal (nodular) heterotopia
Discussion: Heterotopia, or heterotopic gray matter, is the term given to neurons in abnormal locations in the brain. The cause is disrupted migration of neurons as they travel from the germinal matrix toward the cortex, along a roadmap of support cells known as the radial glial fibers. The disease may be inherited or acquired in utero, whether due to trauma, exposure to various toxins (particularly alcohol), infection (especially CMV), or even radiation. Regardless, the end result is damage to the radial glial fibers.
Heterotopic gray matter nomenclature includes both band and nodular forms; nodular subtypes include subependymal and subcortical. As this classification scheme implies, the heterotopic gray matter may either gather in isolated small foci (nodules) or instead group together and form rather linear clusters (bands). All forms are associated with other abnormalities, including agenesis of the corpus callosum, septooptic dysplasia, microcephaly, multiorgan syndromes, and chromosomal abnormalities. While subependymal heterotopia is most common, band heterotopia features the worst prognosis, due to both sheer volume of abnormally located gray matter and more numerous associated anomalies.
Clinically, the most common presentation of heterotopia is that of a young child with developmental delay and seizures. In fact, there is an increased incidence of heterotopia in patients with seizures for which therapy is ineffective.
On imaging, these areas of abnormally situated gray matter show density and intensity characteristics identical to normally situated gray matter.
Is this gray matter functional? Increased cerebral blood flow to these regions on MR perfusion imaging suggests that this is in fact functioning gray matter. However, on histologic analysis, the neurons therein are typically dysplastic/immature, with fewer inhibitory neurons identified.
Treatment options for heterotopia are limited, but surgery may be performed if intractable seizures are present – most commonly in the case of subcortical heterotopic gray matter that has settled in the region of the hippocampus.
References:
- Castillo M, et al., The Core Curriculum: Neuroradiology, Lippincott Williams & Wilkins, Philadelphia, PA, 2002, p.30.
- Golden JA, Harding BN, et al., International Society of Neuropathology, Pathology & Genetics Series: Developmental Neuropathology, ISN Neuropath Press, Los Angeles, CA, 2004, pp. 283-286.
- Osborn AG, et al., Diagnostic Imaging: Brain, Amirsys, Salt Lake City, Utah, 2004, pp. I:1:58-60.
|
