Skull Base Brain Tumor Research

Fully Endoscopic Removal of an Acoustic Neuroma
By Joseph B. Eby M.D

This month we present the case of a 67-year-old male who was referred to the Skull Base Institute for evaluation of a right-sided cerebellopontine angle tumor.

The patient presented 1 month prior to his primary doctor with a complaint of right-sided hearing loss. An MRI scan per-formed in August 2000 demonstrated a 3.5 cm right cerebellopontine angle tumor. On presentation the patient complained of right-sided hearing loss, he denied vertigo, diplopia, or facial asymmetry. The patient had a history of hyper- tension, but denied any other significant past medical history. His past surgical history included surgery for an elbow injury in 1939. The patient's medication included Neurontin 1600mg QD for facial pain and Hydrochlorothiazide 12.5 mg QD for hypertension. The patient's family history was remarkable for hypertension and arthritis, but negative for CAD, Cancer, DM, or Stroke. The patient had a 90 packyear history of smoking and had a mod-erate history of alcohol consumption.

On examination the patient's vital signs included: Ht. 61, Wt. 185, T: 98.8, HR: 70, BP: 170/90, and RR 20. The patient was awake and conversant with no gross focal deficits other than rightsided hearing loss. All other cranial nerves were intact. The patient had a steady gait and a negative Romberg's sign; strength was 5/5 in all extremities. The remainder of his exam was unremarkable.

Review of the patient's MRI revealed a right-sided 3.5 cm mass at the cerebellopontine angle, with an appearance con-sistent with that of an Acoustic Neuroma.

After a discussion of the options, alternatives, and risks the patient and his wife agreed to proceed with a fully endoscopic resection of the tumor.

The patient was taken to the operat-ing room on November 13, 2000 where he underwent a retrosigmoid craniotomy and a fully endoscopic resection of his right-sided cerebellopontine angle tumor. Using both the 0 o and 30 o endoscopes the entire tumor could be visualized and removed with minimal dissection and almost no retraction. Frozen section in the operating room demonstrated the presence of spindle cells, confirming that the tumor was a Vestibular Schwannoma. The facial nerve was identified, however due to mass effect from the tumor the nerve fibers were markedly attenuated. The facial nerve was stimulated and noted to be intact. Once the tumor was removed and hemostasis was achieved, the dura was re-approximated, the bone flap replaced and the scalp was closed in layers. The patient awoke from surgery in the operating room confirming intact mental status and demonstrated a mild (Grade III/VI) facial paresis. The patient had an uneventful recovery and was mon-itored overnight in the surgical intensive care unit. He was then transferred to the floor on post-operative day one, where he was out of bed ambulating and tolerating a regular diet, and was discharged on post-operative day three.

Follow-up at four weeks demonstrat-ed near complete resolution the facial weakness (Grade II/VI), with complete resolution (Grade I/VI) by 3 months post-op.

The improved visualization provided by the endoscope proved extremely valuable during this procedure. The marked attenuation of the facial nerve resulting from tumor compression made the nerve extremely vulnerable to injury during the dissection. We believe that the improved exposure of the entire tumor with minimal retraction or dissection reduces the risk of injury to the brainstem and surrounding cranial nerves, also resulting in more complete tumor removal. This minimally invasive technique allowed for the patients' rapid recovery and resulted in minimal post-operative discomfort.