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|LETTER TO EDITOR
|Year : 2012 | Volume
| Issue : 4 | Page : 444-446
Intracranial lipoma with subgaleal extension: An interesting case report with review of literature
S Rajesh Reddy1, Manas Panigrahi1, Ravi Varma2
1 Department of Neurosurgery, Krishna Institute of Medical Sciences, Secunderabad, India
2 Department of Neuroradiology, Krishna Institute of Medical Sciences, Secunderabad, India
|Date of Web Publication||6-Sep-2012|
Department of Neurosurgery, Krishna Institute of Medical Sciences, Secunderabad
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Reddy S R, Panigrahi M, Varma R. Intracranial lipoma with subgaleal extension: An interesting case report with review of literature. Neurol India 2012;60:444-6
Intracranial lipoma with subgaleal extension causing fenestration of superior sagittal sinus (SSS) and associated with a persistent falcine sinus has been reported only once in literature.  Hence, this case report.
A 13-year-old boy was brought with history of progressively increasing swelling over the scalp in the occipital region of 5 years duration and no other associated symptoms. Child had undergone surgery for a similar swelling at the same site at one month of age. Upon evaluation, a 5 × 6 cm, soft swelling was noted in the midline parieto-occipital region with a positive cough impulse and an overlying scar. Computed tomography (CT) scan and magnetic resonance imaging (MRI) brain showed extra cranial extension of a lesion in the posterior inter hemispheric region through a defect in the calvarium [Figure 1]a-d. The imageological findings were consistent with a lipoma and a band of tissue was noted communicating it with the tectum displacing the latter posteriorly and superiorly. An atretic parietal encephalocele was noted in relation to the tectum. On MR venogram, SSS was found to be fenestrated by the lipoma, a persistent falcine sinus was noted and straight sinus was absent. He underwent repeat surgical excision of the subgaleal part of lipoma for cosmetic reasons. During surgery, the extra cranial part of lipoma was excised and the calvarial defect was closed by opposing the edges of the pericranium around the defect [Figure 1]e. Histopathological findings were consistent with lipoma and no atypical changes.
|Figure 1: T1W axial and T2W sagittal images demonstrate the hyper intense appearing lipoma (arrow heads in a) with both intra and extra cranial parts and a defect in the parietal bone (arrow head on b). An atretic parietal encephalocele (Red asterisk) and a band (arrow) connecting dorsal midbrain with the lipoma are noticeable. MR venogram demonstrates fenestrated superior sagittal sinus (arrow heads in c) and persistent falcine sinus (arrows in d). Per-operative photos show the midline skull defect (arrow heads in e) and the excised extra cranial portion of the lipoma|
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Intracranial lipomas are most commonly located in the inter hemispheric fissure in the region of the pericallosal (50%), ambient or quadrigeminal cisterns (20-25%). Other sites include cerebellopontine, suprasellar, sylvian, prepontine cisterns and rarely over the cerebral hemispheres.  Majority of intracranial lipomas are detected incidentally. Symptoms, if present include those of raised intracranial pressure (due to obstructive hydrocephalus), seizures, and psychomotor retardation and cranial nerve deficits. Those with subcutaneous extension of the intracranial portion present for cosmetic reasons. Half of intracranial lipomas are associated with midline brain malformations of varying severity which include hypoplasia/aplasia of corpus callosum and vascular abnormalities. The latter include distension, kinking or narrowing of arteries and veins, engulfment of cerebral arteries, arteriovenous malformation and aneurysm. Intracranial lipoma with subgaleal extension is rare with isolated case reports in literature.
Intracranial lipomas result from abnormal persistence and mal-differentiation of meninx primitiva.  Secondary dehiscence of the cranium with evagination of a small tuft of meninx primitiva has been proposed as the embryological basis for the extra cranial portion of lipoma. Any insult to the mesenchyme at the level of cranial sutures in the sagittal plane may lead to anomalies of SSS, straight sinus, tentorium and parietal bones which explain the associated anomalies. The anatomic location of the extra cranial part and/or time of appearance of the lipoma determine its relationship to the SSS. A lipoma which develops in the inter hemispheric fissure before the fusion of marginal sinuses to form SSS results in a fenestrated superior SSS as seen in our patient [Figure 2]. Falcine sinus is a normal accessory sinus which is usually obliterated by birth. It provides an alternative venous drainage in the absence of development of straight sinus as occurs in the presence of intra cranial lipoma in the posterior pericallosal region.
|Figure 2: Pathogenesis of intracranial lipoma developing in relation to the corpus callosum. The flow chart on the left demonstrates the rostro-caudal development of corpus callosum in relationship to the lipoma developing from meninx primitiva. The flow chart on the right demonstrates the abnormal persistence and mal development (into lipoma) of meninx primitiva between the marginal veins on either side that fuse to form the superior sagittal sinus. The picture on the bottom right pictorially depicts the final developmental abnormality as seen in the illustrated case|
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Surgery is indicated for only two reasons: cosmetic deformity necessitating removal of the extra cranial portion of lipoma and obstructive hydrocephalus which necessitates a cerebrospinal fluid (CSF) diversion procedure.  Surgical removal of intra cranial lipoma is technically hazardous because of the dense adhesion of lipoma to surrounding structures and due to the disordered course of vessels and nerves through the lesion. In order to minimize the chances of recurrence while removing only the extra cranial part of the lipoma for cosmetic reasons, the surgeon must attempt to obliterate the bony defect by opposing the edges of the pericranium surrounding the defect.
| » References|| |
|1.||Ahmetoglu A, Kul S, Kuzeyli K, Ozturk MH, Sari A. Intracranial and subcutaneous lipoma associated with sagittal sinus fenestration and falcine sinus. AJNR Am J Neuroradiol 2007;28:1034-5. |
|2.||Yildiz H, Hakyemez B, Koroglu M, Yesildag A, Baykal B. Intracranial lipomas: Importance of localization. Neuroradiology 2006;48:1-7. |
|3.||Truwit CL, Barkovich AJ. Pathogenesis of intracranial lipoma: An MR study of 42 patients. AJR Am J Roentgenol 1990;155:855-64. |
|4.||Eghwrudjakpor PO, Kurisaka M, Fukuoka M, Mori K. Intracranial lipomas: Current perspectives in their diagnosis and treatment. Br J Neurosurg 1992;6:139-44. |
[Figure 1], [Figure 2]