A 45-year-old Caucasian, right-handed man presented to our emergency department (ED) with 3 to 4 weeks history of progressive gait disturbances and left lower extremity weakness. His pertinent medical history was negative for any recent history of head trauma, but was significant for a moderate traumatic brain injury (TBI) at the age of 9 years, where he fell off a tree and sustained a closed parietal skull fracture with no posttraumatic cognitive or neurologic deficits. He had no history of seizures, central nervous system infections, stroke, or brain tumor. His neurological exam at admission was significant for left hemiparesis (strikingly more pronounced on lower than upper extremity) and positive left pronator drift testing. A positive Babinski sign could be elicited on the left. He was initially seen in the ED where a magnetic resonance imaging (MRI) showed IE of the right parasagittal parietal bone containing portions of the right precentral gyrus and surrounding brain parenchyma (Fig. 1D). There were no bony deformities upon palpation of scalp.
Noncontrasted computed Tomography (CT) demonstrated a well-circumscribed, 4.3 x 3.7 cm area of osteolysis in the right parasagittal parietal bone, with internal soft tissue attenuation (Fig. 1A-C), complete erosion of the inner table, and noncontiguous lytic changes of the outer table (Fig. 1B, C). MRI with and without gadolinium contrast administration demonstrated a right parasagittal dural defect with intradiploic herniation of the right precentral gyrus (Fig. 1D). There was no restricted diffusion to suggest acute infarction (Fig. 2A-D).
After initial neurosurgical evaluation in the ED, the patient was admitted to the neurosurgical ward and started on dexamethasone 4 mg intravenously every 6 hours. His left lower extremity weakness responded positively to the initial steroids therapy, with partial but transient improvement on his leg weakness to antigravity strength and ambulatory with a rolling walker. He was reluctant to proceed with surgical intervention initially, and elected to continue hospital observation for a few days. Since no sustainable improvement on his strength was seen after 2 days of high-dose dexamethasone treatment, he decided to proceed with surgical intervention.
Under general anesthesia, and using CT-guided intraoperative frameless stereotactic navigation, the area correspondent to the encephalocele was identified and marked. The calvarium was exposed through a bicoronal incision. The bone overlying the encephalocele appeared to be mottled and thin. Cortical brain matter was visualized directly underneath the most thinned portions of the right parietal bone. It appeared pale with no evidence of cortical vasculature, and the usual gyral anatomy had been lost. Starting from the areas of bone dehiscence, the craniectomy was then extended centrifugally until identification of the normal inner table surrounding the whole encephalocele. Once the margins of the encephalocele were completely identified and dissected, a large craniotomy incorporating the bone defect was completed using high-speed craniotome (Fig. 3). Despite an extensive stellate-shaped dural opening and encephalocele decompression, we were unsuccessful on reducing the encephalocele through the pial opening. The pial-arachnoid plane surrounding that area was very sclerotic and firmly adherent to the encephalocele pedicle. Due to the risk of vascular injury to an already friable but apparently still eloquent brain, we decided not to proceed with arachnoidal opening or resection of the encephalocele sac. An expansile duraplasty was completed using a pericranial autograft. The bone flap was replaced with a titanium mesh used for coverage over the craniectomy site.
He tolerated the procedure well and was kept in intensive care unit for 24 hours without complications. Postoperative noncontrasted CT head revealed no ischemic changes on the surrounding parenchyma and adequate reduction of the encephalocele (Fig. 4A-C).
He was transported to the neurosurgery ward in stable condition. He was discharged with mild improvement in left hemiparesis. On 2-month follow-up, his preoperative left leg weakness has greatly improved with near resolution of preoperative hemiparesis.