Left temporal encephalocele as cause of seizures

We present the case of a 45-year-old woman with tonic-clonic seizures since the age of 31. Also, she has episodes of disconnection with myoclonus in the right eye, preceded by a feeling of depersonalization. She is in treatment with carbamazepine with poor control of the symptoms.

The electroencephalogram shows medium voltage sharp waves/spikes in the left temporal region.

3T Magnetic resonance imaging (MRI) is performed. It shows an asymmetry between both temporal lobes. On the left side, a herniation of a small part of the anterior temporal lobe is seen. This region also presented high T2 signal and cortical thinning related to encephalomalacia. These findings are consistent with small encephalocele as seizures cause

Encephaloceles are parenchymal protrusions through a focal bone defect in the calvaria. They are an underdiagnosed cause of epilepsy, especially when they affect the anterior region of the temporal lobes [1-3]. Their detection has been increased thanks to neuroimaging advances such as 3T MRI, being in some cases an incidental finding in asymptomatic patients [2,4]. Their pathophysiology is not still well known, with congenital and acquired cases, but also “spontaneous” with no known risk factors [2]. They are also associated with other processes like hearing loss, meningitis, or otorrhea [4].

MRI is the preferred diagnostic method for patients with epilepsy to evaluate the existence of underlying brain abnormalities, like encephaloceles. Tumors, inflammatory processes, vascular malformations, strokes, cortical dysplasias, and mesial temporal sclerosis are other well-known seizure causes [5]. Temporal encephaloceles are seen as a brain herniation through the dura mater and skull. Typically, they occur in the anteroinferior aspect of the temporal lobe. These findings could be subtle, and, to their small size, they could be overlooked in inexpert hands. Knowing patients’ symptoms, EEG results, and where the epileptogenic foci are located, is needed to improve encephaloceles detection. Also, high-field imaging systems and high-resolution T2 sequences of the temporal lobes, are basics to a proper diagnosis. The protruded brain can show encephalomalacia or gliosis. Also, some cases of encephalocele are associated with idiopathic intracranial hypertension [3].

Treatment in drug-resistant epilepsy with temporal encephalocele is surgery. Lesionectomy or anterior temporal lobe resection can be performed. The choice of one treatment or the other is still controversial, and the main determining factor is whether there are other associated findings in the anterior temporal region [1].

Take Home Message: encephaloceles are an underdiagnosed and tractable cause of seizures that require a careful inspection of MR imaging, especially in the anteroinferior region of temporal lobes.

All patient data have been completely anonymised throughout the entire manuscript and related files.