Skull Base Encephalocele and Meningocele
An encephalocele is a rare condition in which there is a small gap within the bones of the skull through which the coverings of the brain, cerebrospinal fluid and sometimes brain tissue can protrude in a small sac-like structure. Encephaloceles can occur in a variety of locations throughout the skull including the base of the skull. They usually arise secondary to an abnormality during fetal development, which results in a small groove along the middle of the skull. Skull base encephaloceles can be located along the forehead, nose or within the sinuses. Some encephaloceles can be large deformities that are immediately visible but others can be very small and go undetected especially when in the nose or sinus cavities.
Although encephaloceles are generally congenital lesions in children, they can also occur in adults as the result of trauma or prior surgery along the skull base where the paper thin bones between the sinus cavities and the skull are disrupted allowing an encephalocele to form. Encephaloceles are also associated with hydrocephalus (the buildup of cerebrospinal fluid within the brain) and with pseudotumor cerbri a condition where the pressures within the skull and brain are abnormally elevated for reasons that are not entirely well understood.
The symptoms of a skull base encephalocele are usually related to the drainage of cerebrospinal fluid through the brain coverings that have been pushed through the bony defect. The coverings of the brain in an encephalocele often become very thin and can develop tears that lead clear drainage from the nostril. Typically the drainage is worsened with straining, bending or exercise. Infection may also develop within the cerebrospinal fluid leading to meningitis. The over drainage of spinal fluid through the encephalocele can also lead to positional headaches.
The diagnosis of a skull base encephalocele is based on your symptoms, physical exam and specialized imaging studies of the brain and skull base. A high resolution CT scan with 3-Dimensional reconstructions will often be obtained to understand the extent of bony destruction and involvement by the encepholcele. The scans also provides detail information regarding the exact size, location and other structures involved by the encephalocele. The scan is often performed with a contrast dye to help identify the presence of any major arteries that could herniate through into the encepholcele. The MRI scan can also help identify the presence of any hydrocephalus, infection or any other anomalies of the brain that can be associated with an encepholcele. In some cases, otolaryngologists and neurological surgeons may employ a MRI or CT scan for frameless stereotactic guidance. The high-resolution CT scan is processed by a computer to create a 3-Dimensional model of the skull base that can be used in the operating room when performing endoscopic minimally invasive skull base surgery.
The primary treatment for a symptomatic skull base encepholcele is surgical repair of the skull defect, reduction of the encephelocele into the skull cavity and repair of the coverings of the brain to eliminate the cerebrospinal fluid leak. Depending on the size, extent and involvement of associated structures by the encepholcele surgical repair can be performed with either traditional open skull base techniques or with minimally invasive endoscopic techniques performed through the nose. Patients that are candidates for minimally invasive endoscopic techniques often experience fewer or no incisions, decreased pain and a shorter length of hospital stay.