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

Discussion

Congenital encephaloceles represent a quite rare neural tube defect; the incidence has been reported to be 1:5000 live births, but it might be even less frequent in North America.[7,12] The incidence of encephaloceles in specific anatomical locations varies significantly according to sex, with occipital encephaloceles more common among female patients, whereas anterior lesions are more common among males.[7,12] Several classification systems have been proposed based on the anatomical location of the encephalocele;[6] the most widely accepted and simple one appears to be that proposed by Matson.[10] According to his classification system, encephaloceles can be separated into basal, sincipital, convexity, and atretic ones.[10] Each of these groups can be further subdivided into subgroups ( Table 1 ). The most commonly found among these groups is the convexity encephalocele, as in our parietal case.[7]

Encephaloceles have been clearly associated with seizures, particularly in lesions located in the temporal lobe. In their case report, Wilkins, et al.,[17] presented a 36-year-old patient with an encephalocele protruding into the right infratemporal region and projecting into the sphenoidal sinus; this patient suffered complex partial seizures. Resection of her encephalocele was uneventful, and the patient remained seizure free. Ruiz Garcia[15] reported on a 30-year-old patient harboring a temporal encephalocele that caused simple partial seizures; this individual underwent a left anterior lobectomy for excision of encephalocele, with an excellent outcome. Similarly, Hyson, et al.,[8] reported on a 12-year-old patient with simple partial and atonic seizures who underwent surgical excision of his right temporal encephalocele along with ipsilateral anterior temporal lobectomy. Likewise, Leblanc, et al.,[9] Hyson, et al., Rosenbaum, et al.,[14] Elster and Branch,[3] and Whiting, et al.,[16] reported cases of temporal encephaloceles in patients with complex partial seizures and in one patient with generalized tonic-clonic seizures who underwent excision of their encephaloceles. Interestingly, the outcome in all of these cases was excellent, with all patients remaining seizure free (follow-up periods ranged from 12 months to 5 years) and only two experiencing some auras postoperatively.

Furthermore, Rosenbaum, et al.,[14] reported two cases of temporal encephaloceles in patients with complex partial seizures; these patients underwent temporal lobectomies and excision of their intraoperatively discovered encephaloceles, and they remained seizure free postoperatively. Yang, et al.,[18] reported on a patient with bilateral temporal lobe encephaloceles who presented with seizures and hearing loss; this patient underwent resection of both encephaloceles and remained seizure free postoperatively, and his hearing fully recovered. Our patient displayed some quite distinctive characteristics in comparison with these others; her age at seizure onset was 56 years, whereas in all the reported cases the seizure onset age range was between 5 and 31 years. In addition, in all of the previously reported cases the location of the encephaloceles was temporal, whereas in our case it was parietal.

Although the vast majority of the reported encephaloceles associated with seizures are congenital in origin, cases of acquired encephaloceles have also been described.[4,5,11] Guettat, et al.,[5] reported on a 32-year-old patient with a right frontoethmoidal meningoencephalocele presenting with partial complex seizures after undergoing a surgical procedure for resection of a right maxillary sinus polyp and an ethmoidectomy 2 weeks earlier. Acquired temporal or frontal encephaloceles may occur as a consequence of surgical procedures, traumatic injuries, or infections.[2,5,13]

Regarding the diagnosis of encephaloceles, it needs to be emphasized that in a significant number of the reported cases the diagnosis was established intraoperatively; their presence had not been suspected preoperatively.[14,15,17] The recent advances in neuroimaging, along with increasing suspicion of this rare but definitely existent pathological entity can enable surgeons to identify these lesions preoperatively. The synergistic contribution of CT and MR imaging to the preoperative workup in patients with partial complex seizures or in high-risk patients who have undergone previous surgical procedures or who have experienced multiple episodes of recurrent meningitis cannot be overemphasized.[5] In our patient the anatomical location of the encephalocele, along with the alarming clinical symptomatology, significantly facilitated its diagnosis. Nevertheless, in cases of small temporal encephaloceles, their diagnosis might be challenging despite high-resolution MR imaging and CT studies.

In regard to the surgical management of encephaloceles in adults presenting with seizures, this appears to be less challenging than the treatment of these lesions in neonates. Blood loss is usually better tolerated in adults and the size of these lesions is significantly smaller than the ones present in neonates.6 Nevertheless, particular attention needs to be paid to the postoperative functional status of the patient while planning the resection of such lesions, as was done in our case. Our patient's encephalocele was critically located in the proximity of the hand motor area; this was implied by her presenting clinical symptomatology and confirmed by intraoperative cortical mapping. Additional preoperative functional imaging such as functional MR imaging could be beneficial in the surgical planning for these procedures. In our patient, magnetic source imaging of evoked sensory potentials verified that the hand sensory cortex was immediately posterior to the encephalocele in the motor cortex.

The use of a frameless neuronavigational system further enhances the accuracy of the procedure and helps not only in identifying the lesion through a smaller exposure but also in localizing the preregistered adjacent functional areas. Intraoperative cortical mapping can delineate the relationship of the encephalocele with the motor cortex and further minimize the chance of postoperative focal deficits. The importance of meticulous dissection of the encephalocele from the adjacent bone and dural defect (as was the case in our patient) cannot be overemphasized. Finally, reconstruction of the dural (if present) and bone defects can be easily accomplished in these cases, as was demonstrated in our patient.

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