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News -> August, 2004 News
James Palmer, MD
Ioana Schipor, MD
Jonathan Cryer, MD
Case Report
A 38-year old woman presented with a history of headaches, left frontal pain, nasal congestion, and intermittent anosmia. Her past medical history was significant for obesity, hypertension, and asthma. Initial outpatient nasal endoscopy revealed a deviated septum and bilateral middle meatal edema.. She was treated with a steroid dose pack, four weeks of antibiotics, and steroid nasal sprays for presumed chronic sinusitis; with continued symptoms, CT scan imaging of her sinuses was performed revealing a bony defect in the roof of the left ethmoid sinus with a soft tissue density suggesting an encephalocele, as well as obstruction and opacification of her left frontal sinus. An MRI scan confirmed the presence of herniated intracranial contents within the left ethmoid cavity. An incidental note was made of an empty sella (Figure 2).
Figure2
The decision was made to proceed with elective surgical management. A lumbar drain was placed and 0.1 mL of 10% fluorescein diluted in 10 mL of the patient's CSF was injected intrathecally as well as frameless stereotactic computer-assisted surgical navigation system was used for localization. The encephalocele was isolated in the area of the left frontal recess, and once adequate exposure of was achieved, the lesion was fulgurated using bipolar cautery to the level of the skull base. An 8 x 6 mm bony defect with copious CSF drainage (Figure 3) was identified, and the resultant defect was repaired with a suitably shaped septal bone graft placed in the epidural space. This was followed by application of fibrin glue and a free septal mucoperichondrial graft, followed by stentin the area of the left frontal recess was then with a custom-tailored silastic sheet. The lumbar drain was maintained for two days postoperatively, with intracranial pressure was monitoring during this time and was with pressures of 20-29 cm H2O. Given our previous experience with spontaneous anterior skull base encephaloceles in the context of elevated intracranial pressure, the patient was started on acetazolamide, 500 mg, which brough intercranial pressures to the range of 13-18 cm H20. She was discharged home on postoperative day#3; gentle debridement was performed 1 week after surgery; her frontal sinus stent was removed in the office after 2 weeks. She remains on acetazolamide four months postoperatively. On follow up, the graft remains in place, the frontal recess is widely patent, and the mucosa is well healed. She is free from headache and facial pain. There is no evidence of CSF leak or recurrent encephalocele.
Figure3
Discussion
This is a case of endoscopic resection of a spontaneous encephalocele with bone graft reconstruction of the skull base. Encephaloceles are defined as herniations of intracranial contents through the skull. They may contain either meninges alone (meningocele) or meninges and brain matter (meningoencephalocele). These lesions can be either congenital or acquired. The most common acquired etiology is iatrogenic following sinus surgery, with other causes being trauma, tumor, and benign intracranial hypertension. As in the case presented here, a strong association has been described between certain encephaloceles and the radiologic finding of an "empty sella."1 It is postulated that, in these cases, elevated CSF pressure exerts pulsatile forces, which cause erosion of already weak regions of the skull base creating defects and, ultimately, encephaloceles.
Anterior skull base encephaloceles are usually discovered following investigation of rhinologic complaints such as nasal obstruction, sinusitis, clear rhinorrhea, or, rarely meningitis. Once identified, prompt surgical intervention is warranted given the theoretical risk of developing meningitis. Pre-operative workup begins with meticulous nasal endoscopy followed by non-contrast sinus CT scan with both axial and direct coronal cuts. Clear rhinorrhea, if present, should be collected and assayed for beta-2 transferrin. MRI is especially helpful in distinguishing between encephalocele and inspissated secretions, in identifying the contents of the sac, and the presence of significant vascularity.2
Classic treatment for encephaloceles involved neurosurgical transcranial approaches, with attendant risks, morbidities and prolonged post-operative recovery courses. External approaches have also been used, though these have the disadvantage of facial scar. In recent years, transnasal endoscopic approaches have become the standard of care. Their low morbidity and excellent success rate make them especially suitable for repair of ethmoid and sphenoid encephaloceles 3. The basic tenets of endoscopic resection are wide exposure of the encephalocele and surrounding skull base via meticulous dissection, resection of the encephalocele flush with the skull base, removal of a rim of mucosa surrounding the skull base defect, and accurate fit of graft material to the defect. Choice of graft material is dictated by defect size and configuration, underlying pathophysiology, and surgeon preference. Free or pedicled mucoperichondrial grafts, fascia, composite turbinate grafts, cartilage grafts, bone grafts, and hydroxyapatite cement have all been used successfully4. While small defects are often adequately treated with pliable graft material such as mucoperiosteum or fascia, larger defects and those found in the context of benign intracranial hypertension probably warrant placement of an epidural bone graft5. Lumbar drains can be used intraoperatively to assist with encephalocele localization (after intrathecal administration of fluorescein) as well as to shunt CSF away from the defect, allowing easier placement of graft material. In the early post-operative period their utility lies in preventing graft-threatening spikes in intracranial pressure due to inadvertent coughing, sneezing, or emesis. The use of acetazolamide has been shown to reduce intracranial pressure via inhibition of CSF production, and is a useful adjuct in patients for whom elevated intracranial pressure is felt to be responsible for encephalocele formation6.
1. Schlosser RJ, Bolger WE. Spontaneous nasal cerebrospinal fluid leaks and empty sella syndrome: a clinical association. American Journal of Rhinology 17(2): 91-96, 2003.
2. Marshall AH, Jones NS, Robertson IJA. Endoscopic management of basal encephaloceles. The Journal of Laryngology and Otology 115:545-547, 2001.
3. Mattox DE, Loury M. Endoscopic management of cerebrospinal fluid leaks and cephaloceles. In Diseases of the Sinuses Diagnosis and Management by Kennedy DW, Bolger WE, Zinreich SJ. BC Decker Inc, 2001, pp 335-340.
4. Costantino PD, et al. Sphenoethmoid cerebrospinal fluid leak repair with hydroxyapatite cement. Archives of Otolaryngology-Head and Neck Surgery 127(5):588-593, 2001.
5. Bolger WE, McLaughlin K. Cranial bone grafts in cerebrospinal fluid leak and encephalocele repair: a preliminary report. American Journal of Rhinology 17(3): 153-158, 2003.
6. Schlosser RJ, Bolger WE. Nasal cerebrospinal fluid leaks: critical review and surgical considerations. Laryngoscope 114: 255-265, 2004.
Figures
Figure 2. Preoperative MRI showing an enlarged, empty sella
Figure 3. Intraoperative view showing skull base defect after encephalocele has been reduced
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