Ataxic Hemiparesis A Pathologic Study C. Miller Fisher, MD patients showed weakand pyramidal signs on one side combined with a cerebellar-like ataxia on the same side. Pathologic study in each case showed an old infarct cavity in the basis pontis at the level of the junction of the upper one third and lower two thirds on the side opposite the neurologic deficit. The basilar artery was patent and the infarcts were probably the result of occlusion of penetrating arteries. This study demonstrates that a lesion of the basis pontis may be associated with a contralateral ataxia that is cerebellar in character. The designation ataxic hemiparesis is suggested for the syndrome. (Arch Neurol 35:126-128, 1978) \s=b\ Three stroke ness Fisher and Cole1 described a in which the stroke main feature was an unusual combi¬ nation of weakness and ataxia involv¬ ing the limbs on the same side. Although none of the cases was studied pathologically, the process was believed to be ischemia rather than hemorrhage. What remained particularly puzzling was the localiza¬ tion of a lesion that could cause both pyramidal and cerebellar signs in the same limbs. It was difficult on the basis of then-current knowledge to postulate a single site along the cere¬ bral neuraxis where pyramidal and cerebellar signs would not be contralateral to each other. In 1965, syndrome Accepted for publication Aug 29, 1977. From the Neurology Service, Massachusetts General Hospital, and the Department of Neurology, Harvard Medical School, Boston. Reprint requests to Department of Neurology, Massachusetts General Hospital, Fruit St, Boston, MA 02114 (Dr Fisher). Three cases of the syndrome have been examined pathologically revealing a lesion in the upper basis pontis contralateral to both the pyramidal and the cerebellar signs. These cases are the subject of the now present clinicopathologre report. REPORT OF CASES Case 1.—A hypertensive man, aged 82, experienced a transient episode of weak¬ ness of the left arm and unsteadiness of gait one week before admission. On the day of admission, his left side became almost completely paralyzed and the patient felt dizzy and vomited once. On arrival in the Emergency Department four hours later, return of power had begun. The patient alert and oriented. There was a fine horizontal nystagmus on lateral gaze to each side and a coarse vertical nystagmus on gaze upwards. Examination showed slight weakness of the left side of the face, slight dysarthria, and deviation of the tongue to the left. Power in the left upper and lower extremities was 7/10 of normal. The tendon reflexes were brisker and there was a Babinski sign on the left side. The finger-nose and heel-knee-tibia tests re¬ vealed an intention tremor and a slow irregular dysmetria on the left side. The blood pressure was 170/90 mm Hg. The CSF was normal. Recovery was satisfac¬ tory, and in six weeks the patient was able to return home to live by himself. He died 3'/2 years later of pneumonia complicating senile dementia. Neuropathologic Findings.—The brain showed advanced cortical atrophy. The large cerebral arteries, although moder¬ ately atherosclerotic, were patent. On sectioning the brain no lesions were found in the cerebral hemispheres. In the right upper basis pontis at about the junction of the upper one third and lower two thirds of was Downloaded From: http://archneur.jamanetwork.com/ by a UQ Library User on 06/18/2015 the pons, there was a linear irregular cavitation extending from near the surface of the pons to the region of the medial lemniscus posteriorly (Fig 1). It measured 7 mm in an anteroposterior direction, 3.5 to 6 mm transversely, and 5 mm vertically. A small basilar branch artery that ran to the region of the infarcì showed a thick plaque of yellow atherosclerosis at its junction with the basilar artery. Case 2.—A hypertensive man, aged 54, awakened one morning unable to walk without falling. Speech was thick but there was no headache, dizziness, or dysphagia. His condition had improved slightly upon admission to the hospital two weeks later when examination showed an alert, respon¬ sive man with slight to moderate dysarthria. The pupils were equal and reacted to light. The extraocular movements were full with a brisk horizontal nystagmus on lateral gaze to each side and vertical nystagmus on gaze upwards. The face moved symmetrically. Rapid lingual move¬ ments were slow. The left arm and the left leg proximally were slightly weak, while the left toes and ankle were very weak. The tendon reflexes were brisker and there was a Babinski sign on the left side. Sensation was intact to pin, touch, joint-position, and vibration. On the finger-nose and heelknee-tibia tests there was a moderate cere¬ bellar ataxia. Rapid movements of the left extremities were irregular, slow, and clum¬ sy. On the Romberg test swaying was excessive. On attempting to walk, the patient listed and staggered to the left and had to be supported. The left foot scuffed the floor. The patient cried on seeing his family. The blood pressure was 190/110 mm Hg. The CSF was normal. In the following several months recovery was almost complete. Five years later, following a series of transient episodes of aphasia and numb¬ ness of the fingers of the right hand COMMENT The main clinical features of the stroke syndrome were weakness of one side (case 1, slight to moderate of face, arm, and leg; case 2, slight of arm, severe of toes; and case 3, severe Fig 1.-Section of pons tandem infarcts (case 1). showing small Fig 2.-Section of pons showing old infarcì cavity (case 2). lasting 30 minutes, the patient developed a complete right hemiplegia. Angiography showed occlusion of the left internal carotid artery and the patient died one week following an unsuccessful emergency endarterectomy. Neuropathologic Findings.—There was a recent massive infarcì of the left middle cerebral territory. The only old lesion was an irregular cavity measuring 8 mm trans¬ versely, 8 mm vertically, and 5 mm anteroposteriorly in the upper basis pontis at about the junction of the upper one third and lower two thirds. While straddling the midline, it extended mainly to the right and lay posteriorly near the medial lemniscus (Fig 2). A small area of infarction was also present superficially. There were no lesions in the cerebellum. The basilar, both vertebral and right internal carotid ar¬ teries were patent. The penetrating arteries were not examined. Case 3.—A hypertensive man, aged 63, suddenly developed moderate weakness of the left arm and leg one evening. The next morning strength was approximately nor¬ mal but at noon weakness recurred. On Fig 3.-Section of pons showing softening at midline (case 3). examination in the Emergency Depart¬ ment a few hours later, the patient was alert and mentally clear with normal speech. The visual fields were full. The left arm and leg were slightly weak and on the finger-nose and heel-knee tests showed incoordination that was questionably re¬ lated to the weakness. There was no sensory deficit. The next day he was worse with slight left facial weakness, moderate weakness at the left shoulder, and marked weakness of the grip. The tendon reflexes were brisker and there was a Babinski sign on the left. Vertical nystagmus was present on upward gaze. On the third hospital day, the left leg became slightly weaker distally. Sensation was normal and the visual fields were full. The blood pres¬ sure was 180/85 mm Hg. The CSF and electroencephalographic findings were normal. After the third day the patient began to improve, and after six months the only abnormality was slight dragging of the left leg when he was tired. Seven years later the patient had a 45-minute episode of weakness of the right leg and numbness of the right arm. He died from unrelated carcinomatosis eight years later. Neuropathologic Findings—There were only two lesions. In the upper basis pontis at the level of the upper one third and lower two thirds, there was an elongated cavity 7.5 mm anteroposteriorly, 5 mm transversely, and 5 mm vertically (Fig 3). It lay along the midline extending slightly more to the right side and reaching a depth of 10 mm within the pons. The uppermost extremity was 5 mm from the rostral border of the pons. The only other lesion was a 5 mm recent softening in the head of the right caudate nucleus. The basilar artery was atherosclerotic but fully patent. The presence of intermittent symptoms at the onset indicated a thrombotic process. Downloaded From: http://archneur.jamanetwork.com/ by a UQ Library User on 06/18/2015 of arm and slight of face and leg), increased tendon reflexes, a Babinski sign, dysmetria resembling cerebellar ataxia on the finger-nose and heelknee-tibia tests, slowness and incoor¬ dination in rapid alternating move¬ ments, slight dysarthria (cases 1 and 2), vertical and horizontal nystagmus (cases 1 and 2), and vertical nystag¬ mus alone (case 3). There was no numbness, sensory loss, diplopia, vi¬ sual field defect, or mental change. In case 1, dizziness was recorded by one examiner. In brief, there was a pure motor hemiparesis of variable severi¬ ty to which incoordination was added. The stroke deficit reached its maxi¬ mum in one to six days. The lesions lay approximately at the junction of the upper one third and lower two thirds of the basis pontis on the side contralateral to the pyramidal and cerebellar signs. The configura¬ tion of the lesions was variable, and in cases 2 and 3 the localization was at the midline. Since in all cases clinical recovery was excellent, the residual pathologic findings do not necessarily reflect accurately the site of the acute insult that gave rise to the initial clinical syndrome. In each case the basilar artery, although atherosclerotic, was patent. In none of the cases was it possible to prepare serial sections of the spec¬ imen endeavoring to trace out the vascular supply to the territory of the infarcì and identify the vascular occlusion. In case 1, a bead of atheroma lay at the origin of the pene¬ trating artery that ran to the region of the infarcì. In cases 1 and 3 the symptoms fluctuated or were inter¬ mittent over a period of several days suggesting thrombosis rather than embolism. All patients were hyperten¬ sive, a necessary condition for thromboiic occlusion of a penetrating arteryother than in the segment within the basilar wall. It is suspected that the responsible vascular lesions were simi¬ lar to those found in basilar branch occlusion in the lower pons in two previous cases.2 The prognosis for recovery is excelleni explaining the rarity with which satisfactory clinicopathologic corre¬ lation becomes possible. Since the deficit is limited, anticoagulant thera¬ py is not indicated. As already mentioned, infarcts at other sites do not produce the same combination of signs. When the syndrome is recog¬ nized, it can be confidently predicted that a major irreversible deficit is not in the offing. Angiography will not a disclose the small blocked artery and shows normal findings or a demon¬ strated lesion is probably an unrelaied incidenial finding. An imporianí quesiion is wheiher weakness by itself accounted for the incoordination. It is our experience that patients with a sensorimotor or pure motor hemiparesis, whether due to border zone, capsular, or lower pontine lesions, generally show little or no incoordinaiion on ihe fingernose test; at least it is not of the severity in the present cases. Weak limbs are usually not dysmetric. In two personally studied cases of pure motor hemiparesis, one capsular and one lower pontine in origin, the involved leg when elevated with the knee straight wavered up and down 2 to 3 cm but dysmetria was not pres¬ ent. Whether the dysmetria was actually cerebellar in type is a matter difficult to settle, but the resemblance was close. In less severe cases the limbs, during action, show a swinging or swaying incoordination difficult to classify but nevertheless similar to the unsteadiness that may be seen in cases of cerebellar disease. In the absence of specific clinical criieria for a cerebellar deficit, the final answer must be left open. In our laboratory only four cases of upper pontine infarction have been examined in which a good clinicopath- ologic correlation was possible—the three cases described here and the case of dysarthria-clumsy hand syn¬ drome reported in 1967.' In that case, the findings included moderate facial weakness, slight weakness of the arm and leg, a cerebellar type of dysmetria on the finger-nose test, slowing of rapid repetitive movements of the hand and foot, a Babinski sign and slight dragging of the leg, all on the right side, moderate dysarthria, and slight imbalance. The similarity with the present three cases is obvious. Moreover the presence of dysmetria in the right arm in association with a left pontine infarcì supporís ihe view íhaí aíaxia may be contralateral in pontine lesions. In a fifth case studied in detail clinically, the pathologic report simply described a 4 mm lacune in the midbasis pontis without further informa¬ tion. There were five other small cere¬ bral infarcts probably unrelated to the stroke. Seventeen years before death, the patient had three brief episodes in one day of staggering and falling to the left after which he remained ataxic. Examination showed slight horizontal nystagmus on left lateral gaze, moderate cerebellar-like ataxia of the left arm and leg, good strength in the left arm, buckling of the left knee on walking, moderate weakness of dorsiflexion of the left toes and ankle, enhanced tendon reflexes on the left side, a left Babinski sign, and listing to the left on the Romberg test. Recovery was almost complete in a month. Although the information is incomplete, this case clearly fits the syndrome under discussion. From consideration of these four (five) cases, it is obvious that with infarction of the upper basis pontis the hemiparesis is variable in distribu¬ tion and severity. The reason for the variation is probably anatomical in that the compact corticobulbar and Downloaded From: http://archneur.jamanetwork.com/ by a UQ Library User on 06/18/2015 corticospinal tracts as they leave the cerebral peduncles become dispersed by the pontine nuclei with the result that different motor bundles may be damaged by lesions placed slightly differently. In the internal capsule, lower pons, and pyramid the fibers are closely congregated with a tendency for the face, arm, and leg to be uniformly involved. Cerebellar signs are a more constant part of the syndrome and may affect mainly the arm or the leg or both. On the basis of the present clinicopathologic experi¬ ence, it is proposed that the term ataxic hemiparesis be used for this syndrome to supplant the previous designation—homolateral ataxia and crural paresis.1 This study has furnished the solu¬ tion to an old neurologic problem—the site of the lesion responsible for ipsilateral pyramidal and cerebellar signs. The combination is not limited to vascular lesions but may be met with¬ in tumors and in demyelinating processes involving the pons. Specula¬ tion on the mechanism underlying the contralateral cerebellar signs is limited to the suggestion that either the pontine nuclei sending fibers to the opposite cerebellar hemispheres are damaged or crossing fibers from the opposite pontine nuclei are inter¬ rupted. In either case it is not clear why the cerebellar signs are not bilat¬ eral. This study was supported in part by grant NS05152 from the National Institute of Neuro¬ logical and Communicative Disorders and Stroke. References 1. Fisher CM, Cole M: Homolateral ataxia and crural paresis: A vascular syndrome. J Neurol Neurosurg Psychiatry 28:48-55, 1965. 2. Fisher CM, Caplan LR: Basilar branch occlusion: A cause of pontine infarction. Neurology 21:900-905, 1971. 3. Fisher CM: A lacunar stroke: The dysar- thria-clumsy hand syndrome. Neurology 17:614\x=req-\ 617, 1967.