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Show Journal of Clinical Neuro- ophlhalmology 10( 4): 287- 290, 1990 Isolated One- and- a- Half Syndrome with Pontine Cavernous Angioma: Successful Surgical Removal Eric C. Raps, M. D., Steven L. Galetta, M. D., Joseph T. King, Jr., M. D., Anthony T. Yachnis, M. D., and Eugene S. Flamm, M. D. 19 1990 Raven Press, Ltd., New York We report a patient with a pathologically proven pontine cavernous angioma and a horizontal one and a half syndrome. Following recurrent hemorrhages, the vascular malformation was removed from the dorsal pons using microsurgical techniques with partial resolution of the mOtility disturbance. This case demonstrates that vascular malformations of the brainstern parenchyma may be removed, thereby precluding further hemorrhage and facilitating the return of neurologic function. Key Words: Cavernous angioma- One- and- a- half syndrome- Ophthalmoplegia. From the Departments of Neurology ( E. CR.. S. L. G.), Ophthalmology ( S. L. G.), Neurosurgery ( J. T. K .• E. S. F.). and Pathology and Laboratory Medicine ( ATY.), University of Pennsylvania School of Medicine, Philadelphia. Pennsylvania. U. s. A. Address correspondence and reprint requests to Dr. Steven L. Galetta at Department of Neurology. Hospital of the UniverSity of Pennsylvania. Neurology/ 3rd Floor Gates. 3400 Spruce Street, Philadelphia. PA 19104. U. S. A. 287 Cavernous angiomas ( cavernomas) are congenital thin- walled vascular spaces up to 1 mm or more in diameter ( 1). They are distinguished from other vascular malformations of the central nervous system ( CNS) by their size and the existence of intervening gliotic neural tissue. Cavernous angiomas and arteriovenous malformations are rare in the posterior fossa, but generally involve the pons when occurring infratentorially. Both of these vascular malformations may present with subarachnoid hemorrhage, progressive neurologic signs and symptoms, or even acute obstructive hydrocephalus ( 2). Although asymptomatic cavernous angiomas of the CNS may be followed without surgery, symptomatic lesions are generally evaluated for resection on a case- by- case basis ( 3), Surgical removal of pontine cavernous angiomas, although technically challenging, has been facilitated by the development of microsurgical techniques over the past decade, We report the successful removal of a pontine cavernous angioma in a patient exhibiting a one- and- a- half syndrome that partially resolved postoperatively. CASE HISTORY A 19- year- old woman was in good health until December 1986 when diplopia developed that was worse in left gaze. The patient's diplopia persisted and several weeks later, she experienced the abrupt onset of an occipital headache and decreased hearing. Neurologic examination at that time disclosed a left gaze palsy, decreased auditory acuity bilaterally, and a mild right hemiparesis, Magnetic resonance imaging ( MRI) of the brain 288 E. C. RAPS ET AL. demonstrated an intrapontine bleed and a fourvessel angiogram that suggested a residual pontine vascular malformation. In June 1987, a detailed neurological examination was normal and an MRl brain scan showed resolution of fresh hemorrhage ( Fig. 1A). She remained asymptomatic until 2 years later, when horizontal diplopia developed that was worse on left gaze, with mild right hemiparesis and associated dysesthesias. An MRl brain scan revealed new hemorrhage in the dorsal pons. The patient subsequently had two further episodes of recurrent diplopia and right- sided motor and sensory symptoms. In each instance, MRl scans demonstrated new hemorrhage ( Fig. 1B). In November 1989, she presented to the Hospital of the University of Pennsylvania with demonstrable hemorrhage close to the floor of the fourth ventricle. Examination at that time disclosed a left gaze palsy with an associated left internuclear ophthalmoplegia consistent with a one- and- a- half syndrome ( Fig. 2). Convergence was intact and the patient's gaze palsy could not be overcome by oculocephalic maneuvers. The remainder of the examination was normal. Because of the recurrent hemorrhages and their location, surgical removal was advised. OPERATIVE FINDINGS AND PATHOLOGY The patient was placed in the sitting position and underwent midline suboccipital craniectomy. A B Using microsurgical techniques, the cerebellar ve~ mis was divided and the floor of the fourth ventricle identified. From the midline to the left side of the lower part of the floor of the fourth ventricle was a discrete, posterior bulging, yellow discolored mass. A vertical 1.5- cm incision was made and old bloody fluid was evacuated. Within the remains of previous clot, a tuft of blood vessels was observed. Using bipolar cautery and sharp dissection these vessels were removed completely. During the course of the dissection no changes were noted in any of the brainstem auditory evoked responses ( BAERs). On microscopic examination the vascular malformation consisted of a large tuft of abnormally thin- walled vessels with gliotic neural parenchyma consistent with a cavernous angioma ( Fig. 3). POSTOPERATIVE COURSE The patient did well postoperatively and was discharged home on the 10th postoperative day. Follow- up examination one month later showed a residual left gaze palsy, but resolution of the internuclear ophthalmoplegia. Discussion The four types of vascular malformations that occur in the CNS are cavernous angiomas, capll- FIG. 1. Magnetic resonance ( MR) T1- weighted sagittal images of the brain ( spin echo: TE 20 msec, TR 700 msec). A: Image obtained 6 months following initial presentation With lOW- Signal abnormality in the caudal pontine tegmentum consistent with resolving hemorrhage. B: Repeat MR obtained 3 weeks prior to surgery with high- signal abnormality indicating fresh hemorrhage. Moderate mass effect with encroachment on the floor of the fourth ventricle is seen. SURGICAL REMOVAL OF PONTINE CAVERNOMA 289 FIG. 2. One and a half syndrome. A ( left): Patient attempting right gaze with adduction deficit of left eye consistent with internuclear ophthalmoplegia. B ( right): Patient attempting left gaze with Obvious gaze palsy. lary telangiectasis, venous angiomas, and arteriovenous malformations. Cavernous angiomas may be found supratentorially, infratentorially, or even extraaxially and have recently been reported to occur on a familial basis ( 4). In a review of 36 cases of intracranial cavernous angioma, three were located in the posterior fossa and only one was intrapontine ( 5). When symptomatic and embedded within the parenchyma of the brainstern, angiomas pose a difficult management problem. Drake ( 6) reported five cases of symptomatic arteriovenous malformation of the brainstem and cerebellopontine angle. In his series, surgical removal of the lesions had good results in four cases, with one death. Seifert ( 7) reported the use of C02 laser to assist in the extirpation of a brainstern cavernoma in a 43- year- old woman with progressive brainstem signs. Similarly, Scott et al. ( 8) described the successful evacuation of a pontine hematoma secondary to rupture of a cryptic arteriovenous malformation ( AVM) in a 17- month- old boy. Kashiwagi et al. ( 9) emphasized the utility of magnetic resonance ( MR) imaging in the diagnosis of vascular brainstem malformations in their recent review of five cases. Three patients in this study were treated surgically and two were found to have ve- FIG. 3. Cavernous angioma with numerous dilated vascular channels. Gliotic neuropil is seen at left of figure. ( Hematoxylin and eosin, x200). I Gill Neuro- ophthalmol, Vol. 10, No. 4. 1990 290 E. C. RAPS ET AL. nous angiomas. Four additional patients described in an addendum had cavernous angiomas presenting with progressive neurological deficits secondary to multiple hemorrhages. Although isolated gaze or abduction deficits were reported in this and other reviews of pontine vascular malformations, one- and- a- half syndromes with postoperative improvement have not been previously documented ( 2,9,10). However, Sharpe et al. have described a patient who developed a one and a half syndrome following biopsy of a pontine arteriovenous malformation with subsequent partial resolution ( 11). Previous series, albeit small in number, have emphasized the progressive and fluctuating clinical course often seen with cavernous angiomas involving the brainstem ( 2). The patient we report displayed waxing and waning neurologic signs difficult to distinguish from multiple sclerosis on clinical grounds alone. Preoperatively, our patient had an isolated oneand- a- half syndrome. This motility disturbance was first named and correctly localized by Fisher, ( 12), but reported as a clinical entity years earlier by Freeman ( 13). The syndrome is characterized by unilateral gaze palsy and ipsilateral internuclear ophthalmoplegia. Abduction of the contralateral eye is the only retained horizontal eye movement. The lesion is in the pontine tegmentum and involves simultaneous disruption of the ipsilateral paramedian pontine reticular formation ( PPRF) and internuclear fibers of the ipsilateral medial longitudinal fasciculus ( MLF). Inability to induce ipsilateral gaze using oculocephalic maneuvers indicates potential involvement of the abducens nucleus and its interneuronal connections with the PPRF ( 14). Although the number of reported cases of one- and- a- half syndrome is over 50, neuropathologic data have been provided in fewer than 15 cases ( 14,15). To the best of our knowledge, this syndrome has never been described in association with a pathologically proven cavernous angioma that was successfully removed. Wall and Wray ( 10) reported 20 cases of one- and- a- half syndrome and reviewed 29 previously reported cases. The most common identified etiologies in their series were brainstem infarction and multiple sclerosis. Hypertensive hemorrhage has also been reported as an etiology, as well as pontine glioma, cerebellar as-trocytoma, and, on one occasion, " arteriovenous malformation" with no further specifications ( 10). Consideration must be given to surgical removal of cavernous angiomas when these vascular malformations become symptomatic. When located in the parenchyma of the brainstern their clinical course can mimic other disorders, such as multiple sclerosis. RemovaL even from the brainstem parenchyma, may be achieved successfully using microsurgical techniques with elimination of the risk of future hemorrhage and modest improvement in symptoms a distinct possibility. REFERENCES 1. Russell DS, Rubinstein LJ. Pathology of tumors of the nervous system, 4th ed. 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