Background Brain infarction secondary to stenosis of the posterior cerebral artery is uncommon. We report a patient with midbrain infarction and symptoms of both Benedikt’s and pupil-sparing oculomotor palsy syndromes secondary to posterior cerebral artery stenosis.
Case Description A 51-year-old woman developed diplopia, left ptosis, and right hemiataxia and hyperactive tendon reflexes. Pupils were equal and reactive. Radiological examination revealed stenosis of the posterior cerebral artery and a left-sided midbrain infarct.
Conclusions Stenosis of the posterior cerebral artery may cause only midbrain infarction and may be responsible for Benedikt’s and pupil-sparing oculomotor palsy syndromes.
Symptoms from posterior cerebral artery (PCA) stenosis are uncommon and are usually secondary to ischemia of the distal territory of the vessel and include visual and sensory disturbances.1 This report describes a patient with brain stem symptoms (Benedikt’s syndrome and pupil-sparing oculomotor palsy syndrome) secondary to proximal PCA stenosis. We believe this report is of interest because it adds to previously described PCA stenosis symptomatology, and it provides a thorough neuroradiological evaluation of Benedikt’s and pupil-sparing oculomotor palsy syndromes.
A 51-year-old white woman with a history of hypertension and non–insulin-dependent diabetes mellitus presented to the emergency department with diplopia. Earlier that day, she had developed horizontal diplopia, numbness in the right side of the face, and a sensation of weakness in the right arm. Within 2 to 4 hours she had developed complete ptosis of the left eye.
On the day of onset, she was alert and oriented. Optic discs and visual fields were normal. Complete ptosis was present on the left. The right eye moved fully. The left eye deviated down and out and could not gaze up or to the right. The left pupil was 1 mm larger than the right pupil, and left pupillary light reaction was sluggish. Touch sensation was decreased on the right side of the face, but facial pain sensation was intact bilaterally. Facial movement, hearing, speech, and extremity strength were normal. Intention tremor was present in the right arm and leg, and gait was ataxic. Tendon reflexes were slightly hyperactive on the right, and the right plantar response was extensor. Vibratory, touch, and pain sensations were normal in both arms and legs.
One week later when examined by one of the authors (G.W.D.), the patient had pupil-sparing left oculomotor nerve palsy, right hemiataxia, slightly hyperactive tendon reflexes on the right, and flexor plantar responses.
Magnetic resonance imaging (MRI) of the brain was performed with a 1.5-T system (Signa; GE Medical Systems) on the 10th hospital day. Axial T2-weighted (repetition time, 3600 milliseconds; echo time, 102 milliseconds) spin-echo images revealed a well-defined, hyperintense, left-sided midbrain lesion abruptly terminating at the midline most compatible with infarction (Fig 1A⇓). The midbrain was spared on the 1.5-mm supra-adjacent axial MRI image at the uppermost superior colliculus level (Fig 1B⇓). Brain stem structures involved on MRI included the left third cranial nerve nucleus and fascicles, medial longitudinal fasciculus, red nucleus, substantia nigra, and cerebral peduncle. MRI revealed no additional brain stem, cerebellar, or cerebral lesion. Towne projection of a left vertebral cerebral arteriogram demonstrated a high-grade distal left PCA peduncular segment stenosis (Fig 2⇓) at the level of origin for small, penetrating brain stem branches.
Ischemic infarction in the territory of the PCA is usually secondary to total occlusion of the vessel.2 The clinical features vary and may include pure hemianopsia,2 resemble middle cerebral artery occlusion,3 4 or be restricted to thalamic disturbances.5 Symptoms of PCA stenosis are uncommon. Pessin et al1 reported the first series of patients with angiographically proven PCA stenosis. The major clinical features were transient ischemic attacks with contralateral visual symptoms and, in some patients, contralateral sensory symptoms. Only two of the six patients had permanent neurological deficits, and in both patients they were contralateral visual field disturbances.
Our patient is unique because only brain stem symptoms were present. Symptoms of medial temporal and occipital lobe ischemia were absent. Ipsilateral oculomotor nerve palsy and contralateral ataxia and corticospinal tract findings are consistent with Benedikt’s syndrome.6 Previous reports of Benedikt’s syndrome6 did not establish an arterial pathology. Our patient with signs of Benedikt’s syndrome had clear midbrain infarction with involvement of red nucleus, cerebral peduncle, oculomotor fascicles, and lower oculomotor nucleus shown by MRI. Multiple small, peduncular arterial branches arise from the proximal PCA and immediately penetrate the ipsilateral cerebral peduncle to supply the corticospinal and corticobulbar tracts, substantia nigra, red nucleus, third and fourth cranial nerve nuclei, and other ipsilateral midbrain structures.7 Our patient’s high-grade PCA peduncular segment stenosis visualized by vertebral arteriogram likely resulted in origin occlusion of several of these small, penetrating branches and subsequent midbrain infarction. MRI demonstrated midbrain sparing at the level of the upper superior colliculus and Edinger-Westphal nucleus, thus preserving pupillary parasympathetic innervation. While highly stenotic, the PCA remained patent with sparing of more distal brain territories.
Later in this patient’s course, the pupillary function became normal, even though a complete external oculomotor nerve palsy persisted. Previous reports of pupil-sparing oculomotor nerve palsy8 9 have established that intra-axial midbrain infarction similar to that in this patient may have been responsible. This report establishes PCA stenosis as one type of arterial pathology responsible for the syndrome.
The clinical features of this patient provide additional symptoms to the syndrome of PCA stenosis, and their recognition may hasten the diagnosis of PCA stenosis and appropriate treatment.
- Received January 9, 1995.
- Revision received February 22, 1995.
- Accepted February 22, 1995.
- Copyright © 1995 by American Heart Association
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