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Show Journal of Clinical Neuro-ol'hlhallllolog,y 13(3): 218-219, 1993. Letters to the Editor Delayed Oculomotor Palsy from Focal Subarachnoid Hematoma To the Editor: The best-recognized cause of pupil-involving third nerve palsy is an aneurysm at the junction of the internal carotid and posterior communicating arteries; less commonly the distal basilar artery is involved (1-5), We report a case of oculomotor palsy occurring 3 days following rupture of an anterior communicating artery aneurysm, secondary to focal subarachnoid hematoma, Case Report: A 37-year-old man experienced severe headache, nausea, and vomiting, which progressed to loss of consciousness, Upon arrival at out institution, pupils were equally round and briskly reactive. Immediate brain CT revealed a subarachnoid hemorrhage, greatest in the left paramesencephalic cistern (Fig. 1). Three days later, the patient regained consciousness and a complete left third nerve palsy was present. Cerebral angiography demonstrated a large anterior communicating aneurysm feeding from the left internal carotid and projecting inferiorly toward the right (Fig. 2). The next day, via an interhemispheric approach, the cisternal blood was removed and the aneurysm clipped successfully. Immediately upon recovery from anesthesia, the third nerve palsy had completely resolved. Comment: Anterior communicating aneurysm is a rare cause of third nerve palsy. Lane and Tonn (2) found no oculomotor palsies in 176 cases of anterior communicating aneurysm. By virtue of anatomy, anterior communicating aneurysms are unlikely to cause third nerve defects by direct compression. Possible mechanisms by which oculomotor nerve injury may result from anterior communicating aneurysms include midbrain hemorrhage secondary to rapidly enlarging supratentorial hematoma, compression of the brainstem from sudden intraventricular hematoma, and compression of the nerve against the tentorial edge in uncal herniation (4). In the present case, interpeduncular cistern shift 218 to 1993 Raven Press, Ltd .. !'.ew York was seen by CT on the day of hemorrhage. Since the oculomotor palsy was not present until the patient had regained consciousness, uncal herniation is an unlikely cause. The delayed onset of the third nerve palsy may result from the osmotic tonicity of the surrounding blood, deleterious effects of concentrated blood breakdown products, or ischemia from compression of small nutrient arterioles of the nerve (4). The immediate recovery of the oculomotor palsy after surgical evacuation of the hemorrhage suggests that the cranial neuropathy was due to conduction block rather than axonal degeneration or intraneural hemorrhage (3). Focal subarachnoid hemorrhage from anterior communicating artery aneurysm is an unusual case of third nerve palsy. Early surgical decompression of local cisternal blood may maximize the prognosis for rapid and complete recovery. Teng-Yuan Shih, M.D. Department of Neurosurgery Chang Gung Memorial Hospital Kaoshiung, Taiwan, ROC FIG. 1. Contrast~enhanced brain CT shOWing left paramesencephallc hematoma (arrow) with mass effect. LETTERS TO THE EDITOR 219 FIG. 2. Cerebral angiogram, left AP view. Arrow demonstrates large anterior communicating artery aneurysm. REFERENCES 1. Bartleson JD, Trautmann Je, Sundt TM Jr. Minimal oculomotor nerve paresis secondary to umuptured intracranial aneurysm. Arch NeuroI1986;43:1015-20. 2. Laun A, Tonn J-c. Cranial nerve lesions following subarachnoid hemorrhage and aneurysm of the circle of Willis. Neurosurg Rev 1988;11:137-41. 3. Creenspan B, Reeves AG. Transient partial oculomotor nerve paresis with posterior communicating artery aneurysm: a case report. JClin Neural OphthalmoI1990;10:5fh'l. 4. Meyer YJ, Paine JT, Batjer HH. Focal subarachnoid hematoma: an unusual cause of delayed third cranial nerve paralysis. Surg NeuroI1990;34:169-72. 5. Soni SR. Aneurysms of the posterior communicating artery and oculomotor paresis. JNeural Neurosurg Psychiatry 1974; 37:475-84. JClin Neuro-ophthalmol, Vol. 13, No.3, 1993 |
