Journal of Neuro-Ophthalmology, September 1987, Volume 7, Issue 3

Magnetic resonance imaging and the "one-and-a-half" syndrome: a case report.

A patient is described who had magnetic resonance imaging (MRI) findings of a left paramedian pontine ischemic stroke. It was associated with right motor sensory and left cerebellar dysfunction and the "one-and-a-half" syndrome of Fisher.

Journal of Clinical Neuro-ophfhalmology 7(3):161-164, 1987. Magnetic Resonance Imaging and the "One-and-a-Half" Syndrome: A Case Report M. Hommel, M.D., J. M. Gato, M.D., P. Pollack, M.D., F. Borgel, M.D., A. G. Reeves, M.D., G. Crouzet, M.D., J. F. Lebas, M.D., and J. Perret, M.D. ,(. 1987 Raven Press, Ltd" New York A patient is described who had magnetic resonance imaging (MRI) findings of a left paramedian pontine ischemic stroke. It was associated with right motor sen­sory and left cerebellar dysfunction and the "one-and-a­half" syndrome of Fisher. Key Words: One-and-a-half syndrome-Pons-Mag­netic Resonance Imaging (MRI). From the Clinique Neurologique (M.H., J.M.G., P.P., F.B., J.P.), and the MRI Unit (G.c., J.F.L.). Centre Hospitalier Uni­versitaire, Grenoble, France, and the Section of Neurology, Dartmouth-Hitchcock Medical Center (A.G.R.), Hanover, New Hampshire. Address correspondence to Alexander G. Reeves, M.D., Sec­tion of Neurology, Dartmouth-Hitchcock Medical Center, Han­over, NH 03756, U.S.A. Address reprint requests to M. Hommel, Clinique Neurolo­gique, C.H.R.U. Grenoble, La Tronche, 38043 Grenoble Cedex, France. 161 The "one-and-a-half" syndrome was described by Fisher (1) as a lateral gaze palsy on the side of the lesion and a contralateral internuclear ophthal­moplegia so that the ipsilateral eye is fixed in mid­position and the contralateral eye can only abduct. It is associated with a unilateral lesion in the lower part of the dorsal pontine tegmentum affecting the ipsilateral medial longitudinal fasciculus, ipsilat­eral paramedian pontine reticular formation, and/ or the abducens nucleus (1-4). We report a case of the "one-and-a-half" syndrome in which magnetic resonance imaging (MRI) was used to demonstrate the anatomical boundaries of the lesion. CASE REPORT A 56-year-old hypertensive man with peripheral vascular disease complained of blurred vision for 48 h. He was admitted after the rapid onset of oc­cipital headache and brief loss of consciousness. On examination, his sensorium was normal. A right hemiparesis was present affecting the face and the arm less severely than the leg. A right Ba­binski sign was present. A severe right hemisen­sory loss and a left cerebellar ataxia were present. The patient was dysarthric and dysphagic. Both eyes were spontaneously in neutral position. Left voluntary and pursuit horizontal gaze were abol­ished. Only the right eye could move in abduc­tion, and a right beating nystagmus appeared after a 20° course, Vertical gaze was normal but conver­gence was limited. The pupils were 1 mm in diam­eter and reacted to light. The patient was considered to have the one­and- a-half syndrome. A computerized tomog­raphy (CT) scan was normal. The patient was hep­arinized. One day later, hematemesis and inhala­tion pneumonia complicated the situation. The /62 M. HOMMEL ET AL. patient's neurologic state deteriorated. A right total hemiplegia and sensory loss were present. Right decerebrate posturing occurred. The tongue de­viated toward the right on protrusion. There was severe dysphagia and dysarthria and left periph­eral facial weakness. Spontaneous ocular bobbing was present, and the eyes were skewed, with the right lower. A 10° exotropia of the right eye was present. There was no voluntary and pursuit hori­zontal gaze of the left eye, and the oculocephalic maneuver and unilateral cold water irrigations gave no response. Voluntary and pursuit abduc­tion of the right eye were full, with right-beating nystagmus. The right eye returned slowly from the abducted to the midposition and could not cross the midline to the left side with either volun­tary or pursuit gaze. A right eye adduction of 15° could be elicited by left-ear cold caloric irrigation and by the oculocephalic maneuver. Vertical gaze movements were full, and an up-beating nys­tagmus was observed on upward gaze. Conver­gence was preserved. Ocular bobbing and skewed deviation disappeared after 2 days, but the other ocular disturbances remained for 1 month. MRI FINDINGS An MRI study was performed 24 days after the stroke. A CGR Magniscan 5000 was used with a superconducting magnet operating at a field strength of 0.5 Tesla corresponding to a proton resonance frequency of 21.3 Hz; 8-mm axial and sagittal T2MR images (spin echo TE/TR = 60 and 120/2000) were obtained. An area of increased signal was observed in the upper two thirds of the ventral pons. This area prolonged through the tegmentum at the level of the midpons as far as the fourth ventricle (Fig. 1). On the axial planes at the level of the lower pons, the area of increased T2 was localized in the left paramedial tegmentum but did not reach the periventricular region (Fig. 2). An isolated in­creased T2 region was also observed in the left middle cerebellar peduncle. At the level of the midpons, the increase in T2 area affected the ven­tral pons and the paramedial left tegmentum; it also reached the fourth ventricle and the left part of the periventricular region (Fig. 3). The lesion also affected the ventral part of the left midbrain but did not reach the tegmentum at this level. COMMENTS n>~;':'1t, the rapid onset of the symptoms, .' ;!":' tl)cal increase in T2 FIG. 1. Medial saggital view in T2-weighted sequence (first echo, TE, 60 ms). The large arrows outline the lesion, which involves the upper two thirds of the pontine base and, at midpons, extends with the para­median tegmentum reaching the floor of the fourth ventricle (IV) and aqueduct (a). The small arrows indi­cate the levels of the axial planes of Figs. 2 and 3, values with MRI are consistent with infarction. Right hemiplegia and hemianesthesia indicated in­volvement of the left corticospinal tract and medial leminiscus. Paralysis of abduction of the left eye suggests destruction of either the left paramedian pontine reticular formation (PPRF), the nucleus abducens, or the motor neuron root fibers. The as­sociated absence of right eye saccades to the left is in favor of a lesion in the left pontine paramedian reticular formation (7-10). Abduction of the right eye with caloric stimulation indicated preservation of the right PPRF, the right abducens nucleus, or both (5). The absence of adduction of the left eye with preservation of convergence and nystagmus in the right eye on abduction localizes the lesion in the left medial longitudinal fasciculus (6). The eso­tropia of the right eye and the absence of conju­gate gaze to the left are in favor of a lesion of the left pontine paramedian reticular formation (7,8,9,10). Figure 4 schematically illustrates the MRI extracted total cross-sectional area of infarc­tion at the lower pontine level. Destruction of the "ONE-AND-A-HALF" SYNDROME 163 FIG. 2. Axial plane of midpons in T2­weighted sequence (first echo, TE, 60 ms) showing extension of lesion (small arrow) in left paramedian region en­compassing PPRF and MLF. An iso­lated lesion in left brachium pontis is also present (large arrow); b, basilar artery; IV, fourth ventricle). left medial longitudinal fasciculus, paramedian pontine reticular formation, corticospinal tract, and medial leminuscus was accurately confirmed by MRI. Caplan and Goodwin described the syndrome of lateral tegmental brainstem hemorrhage with ipsilateral gaze palsy, ipsilateral internuclear ophthalmoplegia, miosis ipsilateral to the lesion, ipsilateral limb ataxia of the cerebellar type, con­tralateral hemiplegia, and contralateral severe hemisensory loss (11). Our patient recapitulated these signs. The ipsilateral cerebellar ataxia was associated with infarction of the middle cerebellar peduncle as confirmed by MRI. The right hemipa­resis and hemisensory loss observed on admission were related to left pontine base and midbrain pe­duncle infarction and medial leminiscus involve­ment in the pons as demonstrated by MRI. This syndrome, as discussed by Caplan and Goodwin, is a topographical syndrome usually associated with hemorrhage; to our knowledge, this is the first report of infarction as the cause of the syn­drome. Occlusion of a variant branch of the basilar artery may have been responsible (12). Our case illustrates that it is not possible on clinical grounds alone to distinguish infarction from hemorrhage of FIG. 3. Axial plane of the midpons in T2-weighted sequence (first echo, TE, 60 ms). Arrows outline the lesion, which extends dorsally from the pontine base to the transition between the fourth ventricle and the aqueduct (a; b, basilar artery). I Clill Nellr"'''pl,lhalmol, Vol. 7. No.3, 1987 164 M. HOMMEL ET AI. l L..~~ _ PIPRF. _ ML _:.__ ~ _ FIG. 4. Schematic cross-section at the level of Fig. 3, showing normal anatomic structures in the right pons and the lesion on the left (CT, corticospinal tract;' ML, medial lemniscus; PPRF, paramedian pontine retic­ular formation; MLF, medial longitudinal fasciculus; b, basilar artery). the pontine tegmentum. The anatomical basis of the syndrome observed in our case was clearly il­lustrated by MRI, elegantly underscoring the value of this technique for delineating small vas­cular lesions in the brainstem. I Clin Nt'uro-ophthulmvl, Vol,;. i'l REFERENCES 1. Fisher CM. Some neuro-ophthalmologic observations. 1 Neural Neurosurg Psychiatr 1967;30:383-92. 2. Pierrot-Deseilligny CH, Chain F, Serdaru M, Gray F, Lher­mitte F. The "one-and-a-half" syndrome. Electrooculo­graphic analysis of five cases with deductions about the physiological mechanisms of lateral gaze. Brain 1981;104:665-99. 3. Prier S, Larmande P, Henin D, Delouvrier H, Masson M. Le syndrome de un et demi de Fisher. 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