Occipital extra- and intracranial lipoencephalocele associated with tectocerebellar dysraphia: case for discussion

Abstract

Y. Yamanouchi ()) Department of Neurosurgery, Kansai Medical University, 10–15 Fuimizono-cho, 570–8507 Moriguchi-city, Osaka, Japan e-mail: yamauchy@takii.kmu.ac.jp Tel.: +81-6-69921001 Fax: +81-6-69916207 The author presented a rare and interesting case in which embryological consideration and pathogenesis of tectocerebellar dysraphia with lipoma was discussed. I felt a strong similarity between this case and lipomyelomeningoceles in the spine after a first reading. I agreed with almost everything the authors wrote. However, it does not seem to me that the co-existence of the lipoencephalocele and tectocerebellar dysraphia suggests multiple sites of neural closure. Intracranial lipomas can occur in various locations: in the corpus callosum, quadrigeminal area, brainstem, and cerebellum, mainly in the midline. Many of them occur without skull defect and other cerebral malformations. Regarding lipomas, we should consider ordinary lipoencephaloceles or lipomeningoceles totally separately from lipomas, such as those located in the corpus callosum or spinal lipomas without dysraphism. Truwit and Barkovich, cited by the author, stated that intracranial lipomas are congenital malformations that result from abnormal persistence and maldifferentiation of meninx primitiva during the development of the subarachnoid cisterns [3]. But in this case, it is possible that abnormal development occurred earlier than the stage of development of the subarachnoid cisterns. In the dysraphic state, I don’t think there is the same pathogenesis in skin-covered lesions and lesions with the neural tissue exposed. Tarara et al. [2] induced central nervous system malformations in primates by using triamcinolone acetonide. They suggested encephaloceles may result from a combination of mesenchymal and neural tube abnormalities. In this case, considering the coexistence of lipomatous tissue, we may apply the theory of embryogenesis of spinal lipomyelomeningoceles resulting from premature dysjunction, which is that lipomas arise when the cutaneous ectoderm prematurely separates from the neuroepithelium prior to neural fold fusion. Under these circumstances, the surrounding mesenchyme ingresses between the neural tube and overlying cutaneous ectoderm [1].