Spontaneous Motor Cortex Encephalocele Presenting With Simple Partial Seizures and Progressive Hemiparesis

Case Report and Review of the Literature

Kostas N. Fountas, M.D., Ph.D.; Joseph R. Smith, M.D.; Patrick D. Jenkins, Ph.D.; Anthony M. Murro, M.D.

Disclosures

Neurosurg Focus. 2005;19(3) 

In This Article

Abstract and Introduction

Several cases of congenital or acquired temporal encephaloceles have been reported in the literature as the causative mechanism of simple and/or complex partial seizures. In this report the authors describe a rare case of spontaneous parietal encephalocele presenting with simple partial seizures and progressively increasing contralateral upper-extremity motor deficit. The unusual anatomical location of an encephalocele associated with seizures and the delayed seizure onset represent distinctive characteristics in this case. Preoperative imaging included surface electroencephalography, computerized tomography, and brain magnetic resonance imaging. Frameless neuronavigation and intraoperative cortical mapping were used to aid resection of the encephalocele, and the dural and bone defects were reconstructed. The surgical outcome in this case was excellent, and the patient has remained seizure free. The pertinent literature is reviewed in this report.

An association between seizures and encephaloceles, although rare, is well established.[1,5,8,9,11,14–18] There are several reports in the literature describing cases of medically intractable epilepsy, in which the operative findings revealed that small encephaloceles were the epileptogenic focus. In the vast majority of these cases the underlying encephaloceles had remained undiagnosed for prolonged periods and were intraoperatively identified as the cause of usually complex partial seizures.[14,15,17] These encephaloceles were congenital in most of the reported cases;[8,9,14,16–18] however, a few cases of acquired encephaloceles associated with medically refractory seizures have also been described.[4,5,11]

In this communication we report a case of spontaneous motor cortex encephalocele, which presented with progressive hemiparesis and simple partial seizures and was successfully treated at our institution. In addition, we review the pertinent literature. CASE REPORT History and Examination. This 61-year-old Caucasian, right-handed woman was evaluated in our epilepsy clinic for seizures marked by an inability to use her left hand, followed by left thumb jerking that progressed to generalized tonic-clonic seizures. Her seizures had begun 5 years previously and progressively increased in frequency. Initial evaluation revealed dysarthria, left-sided facial weakness, and dysphagia that had started approximately 3 months earlier and had been worsening. Her neurological examination revealed mild facial weakness (motor strength 4+/5) with no other focal abnormalities. She was evaluated periodically in the adult epilepsy clinic for several years. Initially, there was no report of a change in neurological status. On her last visit before surgery, however, the patient reported a slight but definite increase in gripping strength in her left hand. Serial MR images demonstrated no progression of the gliosis or traction on the right lateral ventricle (Fig. 1).

Screen capture showing intraoperative localization of the parietal encephalocele by using a frameless neuronavigation device (MR imaging–based approach).

The patient's medical history revealed no concussion, birth complications, febrile seizures, central nervous system infection, stroke, or brain tumor. Her family history was unremarkable. She was currently receiving 1500 mg levetiracetam per day, and several other anticonvulsive medications (valproate, phenytoin, ethosuximide, and carbamazepine) had been tried previously. Her seizures had been well controlled by her latest medication until recently.

Her laboratory workup included surface interictal electroencephalography and brain MR imaging. Her electroencephalogram demonstrated no abnormalities. Serial MR imaging studies revealed a right parietal defect of the inner table of the skull, with an associated protruding encephalocele. There was also an associated gliotic track creating traction on the right lateral ventricle.

The imaging and electrophysiological findings were extensively discussed with the patient and the option of resection of her encephalocele was offered to her. After considering the advantages and disadvantages of such a surgical intervention, the patient decided to proceed with resection.

After endotracheal induction of general anesthesia, the patient was placed on the operating table in a left semidecubitus position with her torso rolled up approximately 40°. The patient's head was secured in a three-point Mayfield fixation device. Frameless stereotaxy (BrainLAB AG, Heimstetten, Germany) was applied for localization of the encephalocele and of what we thought was motor cortex (based solely on anatomical criteria; Fig. 1). A 10-cm linear skin incision extending from the midline longitudinally to a point just in front of and above her right ear was centered over the encephalocele. A high-speed air drill (Midas Rex; Medtronic, Inc., Minneapolis, MN) was used to make a doughnut-shaped craniectomy circumferentially to the lesion, after meticulous dissection of the exposed encephalocele from the adjacent bone edges (Fig. 2A). The exposed underlying normal-appearing dura mater was cruciated around the encephalocele, and after meticulous dissection the stalk of the lesion was identified (Fig. 2B).

A: Intraoperative photograph showing the doughnut-shaped circumferential craniectomy performed to expose the parietal encephalocele. B: Photograph showing the exposed encephalocele after removal of the overlying bone.

Subsequently, intraoperative corticography was performed and revealed no epileptogenic activity in the area of encephalocele. At that point, cortical motor mapping using direct stimulation was performed. Stimulation (pulse width 1 msec, 4 V, 60 Hz) of a site immediately superior to the encephalocele caused flexion of all the fingers of the left hand (Fig. 3A).

A: Intraoperative photograph showing the area undergoing cortical mapping. Data were obtained using intraoperative cortical stimulation, which identified the ipsilateral hand motor area superior to the encephalocele (sticker 1). B: Intraoperative photograph showing complete removal of the parietal encephalocele.

After completion of the motor mapping, the stalk of the encephalocele was transected en bloc by using bipolar cautery, and was then sent for pathological examination (Fig. 3B). Hemostasis was obtained and the overlying dura mater was closed using 4-0 silk sutures (Fig. 4A). When that was done, a 5 × 6–cm piece of polysorbate mesh was secured with 4-mm absorbable screws. After that, bone putty was used to fill in the cranial defect and then a second outer plate of polysorbate mesh (of the same dimensions) was secured over the bone putty with 4-mm absorbable screws (Fig. 4B). The surgical wound was closed in anatomical layers.

Pathological examination of the resected specimen revealed gliotic and edematous cerebral cortex consistent with encephalocele.

The patient was observed in the intensive care unit for 24 hours and then was transported to the neurosurgical ward for 48 hours, after which she was discharged home. She has remained seizure free (26-month follow-up duration) with no evidence of focal neurological deficits and no other symptoms.

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