Spontaneous Parietal Intradiploic Encephalocele Biology Essay

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Very few cases of intradiploic encephalocele in adulthood have been reported in the literature. We describe a case of spontaneous parietal intradiploic encephalocele presenting with simple partial seizures. Preoperative imaging (CT and MRI) showed brain herniation within the intradiploic space. Diagnosis was confirmed at surgery. Postoperatively the patient recovered from his presenting symptoms.

History and examination A 75-year-old man presented to our clinic with a 1-month history of partial seizures in the right inferior limb. His neurological examination revealed no focal abnormalities. Nothing was found on the examination of his scalp. His medical history revealed type 2 diabetes, high blood pressure, coronary heart disease, hepatitis C, but no head trauma, febrile seizures, stroke, brain tumor ,central nervous system infection. His family history was uneventful.

Neuroimaging Axial bone window CT image depicts a relatively small round defect of the inner table, with a large diplic space, and a very thin outer table in the left parietal parasagittal bone. Axial brain window CT image (semioval center section) reveals small brain herniation through the osseous defect (Fig 1).

Fig.1 Left: Axial bone window CT-approximate 1 cm. centimeter inner table parietal defect is observed, with relatively smooth margins of the intraosseous intradiploic lesion. Also we remark a very thin calvarial external parietal diploes . Right: the parietal osseous defect has marginal sclerosis and contains a small amount of herniated brain.

Magnetic resonance (MR) imaging showed a lesion in the left parietal parasagittal intradiploic space continuous with the left parietal lobe appearing isointense with the normal brain on T1-weighted(Fig.2) and T2-weighted images(Fig.3).

Fig.2 Axial T1w image shows intradiploic extension within the left parietal bone

Fig.3-Axial T2w image shows a signal isointense to the CSF in the left parietal bone

Coronal T2-weighted, sagittalT1-weighted images (Fig.4) shows a defect in the left parasagital parietal bone that contains hypersinal T2 and herniated cerebral tissue . The cerebrospinal fluid is continuous with the subarachnoid space. The underlying parietal lobe had similar signal intensity properties. The superior sagittal sinus is intact.T1-weighted MR imaging with gadolinium revealed no enhancement of the lesion. (Fig.5)

Fig.4: Coronal T2w image(left) reveals the patency of the superior sagittal sinus and the dural discontinuity and brain herniation on sagittal T1w image(right)

Fig.5 Coronal and sagittal T1w contrast-enhanced MR image

Operation After the endotracheal induction of total anesthesia, the patient was placed in a decubitus dorsal position , with the head slightly raised and turned to the right side. An arcuate skin incision was performed and the pericranium was preserved carefully. The exposed underlying paper-thin bone (1 cm diameter) was pulsatile.

We performed a craniectomy around the margin of the bone lesion and we exposed a dural defect of about one cm. in diameter in which a small amount of brain herniated. The superior sagittal sinus was intact. The margins of the dura were carefully dissected and the herniated tissue excised. Dura was reconstructed then with the aid of pericranium, Following local hemostasis the skin incision was closed with separate sutures. Pathological examination of the resected specimen revealed gliotic and normal cerebral cortex.

Postoperative course The patient received 600 mg carbamazepine per day for three months after surgery, and he remained seizure free on his 6-month follow-up.

Discussion

A cephalocele is defined as a protrusion of intracranial contents through a defect in the skull or dura. Cephaloceles are classified by their contents (meningocele, meningoencephalocele, hydromeningoencephalocele) and by the location of the cranial defect through which the herniation occurs. The herniating neural tissue may include meninges, brain parenchyma, ventricles and vascular structures. A cephalocele can result from various causes: infection, trauma, surgery, tumors. Those which develop in absence of such acquired processes are congenital or immediatly postnatal developmental defects termed spontaneous meningoencephaloceles. These type of with a spontaneous character usually occur at the site of a suture, and most of them represent depects of the neural primary or secondary closure.

Parietal cephalocele are very rare (1% of all cerebrospinal malformations and 10% of cephaloceles [5]) and if congenital, they are usually associated with many anomalies such as corpus calosum agenesis, Chiari II, Dandy-Walker malformation.

The intradiploic encephaloceles are also extremely rare, only few cases are mentioned in the literature. In their case report Patil, et al.[9] presented a 64-year-old man with a posttraumatic intradiploic meningoencephalocele after a head trauma. He hit his head with a garage door and 8 months post-trauma he presented with a lump on his head. The authors concluded that their case was a variation of an adult growing skull fracture due to the blunt trauma to the head, an intradiploic arachnoidal cyst containing CSF and brain. Lenthall, et al. [7], also presented a case of a growing skull fracture with the intradiploic extension whitin the occipital and parietal bone in a 6-month-old baby who sustained a head trauma after falling down the stairs, but in this case both inner and outer bone tables were eroded. A'teriitehau, et al. [6] described an intradiploic parietal encephalocele in a 73-year-old woman with no history of significant head trauma, but they attributed the intradiploic defect to a minor trauma, without loss of consciousness , but strong enough to produce the destruction of the inner table and a dural tear. Peters , et al. [5] came to the same conclusion with their patient presenting with coordinative problems in his right leg, also without history of head trauma. Martinez-Lage, et al. [8] reported a frontal intradiploic meningoencephalocele following a dural tear produced during surgery for craniosynostosis. This unusual lesion resembles the mechanism of the growing skull fracture.

Although the majority of reported intradiploic encephalocele are traumatic in origin, four reports found no certain cause for this lesion [1, 2, 3, 4]. In all these cases the lesion was away from the midline and affected only the inner table. One patient [1] with an occult intradiploic encephalocele became symptomatic after a paroxysmal increase in intracranial pressure. In other case [4] presenting with generalized seizure and aphasia, the authors opiniated for the congenital origin of the dural defect, through which the brain herniated.

Among the particularities of our case are included: the location of the lesion (close to the sagittal suture), the absence of significant head trauma, infection or neoplastic history, the integrity of the outer table. The differential diagnosis must be made between an acquired lesion and a congenital one. The location and the absence of an evident cause could suggest that the lesion in our patient was a congenital anomaly. However in a report conducted by Patterson,et al.[10], in all cases of congenital parietal encephalocele there was a global defect of both inner and outer table. The absence of an associated malformation and the aspect of the bone defect suggest that the lesion was acquired, maybe due to a insignificant head trauma.

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