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Show Journal of Nettm- Ophthalmology 18( 3): 204- 205, IWK © 1998 Lippincolt Williams & Wilkins, Philadelphia Isolated Fourth Nerve Palsy From Midbrain Hemorrhage Case Report Steven L. Galetta, M. D., and Laura J. Balcer, M. D. Isolated ocular motor palsies caused by brainstem strokes have been considered uncommon. However, since the development of magnetic resonance imaging ( MRI), the occurrence of isolated ocular motor palsies resulting from brainstem strokes have become more frequently recognized ( 1- 5). We report a patient who developed a fourth nerve palsy contralateral to a small dorsal mid- brain hemorrhage. CASE REPORT A 69- year- old woman with a history of hypertension underwent surgery for removal of a thyroglossal cyst. A few hours after surgery she had difficulty breathing, and a wound hemorrhage was suspected. The patient was returned to the operating room, and the hematoma was drained. After the second surgery, she developed oblique double vision. There were no other neurologic symptoms. She was on Hydrodiuril ( Merck) 25 mg a day. Neuroophthalmologic examination showed a blood pressure of 168/ 100 mmHg in the right arm. Visual acuity was 20/ 20 bilaterally. Visual fields were full. She had bilateral levator dehiscence. Pupils were 4 mm and briskly reactive to light. There was no dilatation lag of the pupils. Motility examination showed an eight- diopter right hypertropia in the primary position. The right hypertropia increased to 12 diopters in left gaze and 16 diopters with right head tilt. There was a 5- diopter right hypertropia in right gaze and with left head till. Vertical fusional amplitudes were Iwo diopters. These findings were consistent with an acquired right superior oblique palsy ( Fig. 1). The remainder of the examination was significant for a mild right pronator drift. However, the reflexes were symmetric and the plantar responses were flexor. MRI scan showed a small focal hemorrhage in the region between the aqueduct of Sylvius and ( he fourth ventricle on the left ( Fig. 2). There was an area of old hemorrhage in the left thalamic region and bilateral, Manuscript received November 1997; accepted November 1997. From ( he Departments of Neurology and Ophthalmology, University of Pennsylvania Medical Center, Philadelphia. Pennsylvania, U. S. A. Address correspondence and reprint requests to Dr. Steven L. Galetta, Department of Neurology. 3 W. Gales/ 3400 Spruce Street, Philadelphia, PA 19104, U. S. A. periventricular high signal abnormality consistent with small vessel ischemic disease. The superior oblique palsy did not improve over the next 6 months, and she was treated with prismatic glasses. Follow- up MRI scan at that lime showed a small area of hypointensity on gradient echo images consistent with hemosiderin from a prior bleed. There was no evidence of enhancement or methemoglobin. DISCUSSION Our patient had an isolated fourth nerve palsy related to a contralateral dorsal mid- brain hemorrhage. She did have a mild right pronator drift, but this finding was likely related to a prior vascular insult. Brain stem strokes may be a more frequent cause of isolated ocular motor palsies than previously recognized. Numerous reports have documented the association of isolated ocular motor palsies and brain stem strokes since the development of MRI ( 1- 7). Thus far, reports of isolated or nearly isolated fourth nerve palsies from brain stem stroke have been rare ( 5,6). Kim et al. reported a patient with a right superior oblique palsy and right facial numbness from a left mid- brain lesion ( 5). Mon recently described a 70- year- old patient with an isolated fourth nerve palsy from a left mid- brain tectal hemorrhage as documented by a brain computed tomography ( CT) scan ( 6). A follow- up CT scan showed a calcified lesion suggesting an underlying vascular anomaly. Although it may be difficult to distinguish a nuclear fourth nerve palsy from a fascicular one ( 8), the MRI lesion of our patient suggests that the proximal fourth FIG. 1. External photograph demonstrating right superior oblique palsy as the patient looks down and to the left. 204 ISOLATED FOURTH NERVE PALSY 205 FIG. 2. T2- weighted magnetic resonance image 2 weeks after ictus demonstrates left tectal hemorrhage with met-hemoglobin ( arrow) posteriorly and hemosiderin ( dark area) anteriorly. nerve fascicle was primarily involved. The increased recognition of brain stem lesions manifesting with isolated ocular motor palsies has lowered our threshold for imaging such patients. The mild pronator drift found in outpatient was one factor in our decision to obtain an MRI scan. However, this finding was not a manifestation of the new hemorrhagic mid- brain lesion. Further analysis will be necessary to determine the role and indications for obtaining MRI in those patients with isolated ocular motor palsies. REFERENCES I. Hop!' HC, Gulmann L. Diabetic 3rd nerve palsy: evidence for a mesencephalic lesion. Neurology 1990; 40: 1041- 5. 2. Donaldson D, Rosenberg N. Infarction of abdncens nerve fascicle as cause of isolated sixth nerve palsy related to hypertension. Neurology 1988; 38: 1654. 3. Johnson LN, Hcpler RS. Isolated abdncens nerve paresis from intrapontine fascicular abdncens nerve injury. Am J Ophthalmol 1989; 108: 459- 61. 4. Fukutake T, Hirayama K. Isolated abdncens nerve palsy from pontine infarction in a diabetic patient. Neurology 1992: 42: 2226. 5. Kim JS, Kang JK, Lee SA, I. cc MC. Isolated or predominant ocular motor nerve palsy as a manifestation of brain stem stroke. Stroke 1993; 24: 581- 6. 6. Mon Y. Midbrain hemorrhage presenting with trochlear nerve palsy- a case report: Rinsho Shinkeigaki 1996; 36: 71- 3. 7. Hosghiguchi S, Ogasawara N, Igaki T. Persistent isolated abdncens nerve palsy from pontine infarction confirmed by gadolinium DPTA enhanced MR. Rinsho Shinkeigakii 1994; 34: 72- 6. 8. Brazis PW. Palsies of the trochlear nerve: diagnosis and localization- recent concepts. Mayo Clin Proc 1993; 68: 501- 7. .1 Neiim- Oplillialiiml. Vol. IS. No. .1 I99S |
