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Show Journal of Clulleal Neuro- ol, ltthaimoioxy 12(]): 17- 20, 1992. Acute VIth Cranial Nerve Dysfunction In Multiple Sclerosis Evaluation by Magnetic Resonance Imaging John W. Rose, M. D., Kathleen B. Digre, M. D., Sharon G. Lynch, M. D., and Ric H. Harnsberger, M. D. © 1992 Raven Press, Ltd., New York VI'h nerve palsy is not frequently considered a presenting sign of multiple sclerosis ( MS); however, MS has been documented as a fairly common cause of VI'h nerve dysfunction. In the present study we have evaluated the clinical features and magnetic resonance imaging ( MRl) findings in four MS patients with acute VI'h nerve palsies. Diplopia as a result of acute VI'h nerve palsy was the prominent symptom leading to the diagnosis of MS in all of the individuals. Other signs specifically localizing to the ipsilateral brainstem were absent in these patients. Cranial MRl revealed multiple white matter lesions with a periventricular predominance in all four patients and pontine white matter lesions in three of the patients. These lesions were either adjacent to the VI'h nerve nucleus or involved the fasciculus of the VI'h nerve or both. Key Words: Magnetic resonance imaging- Multiple scierosis- VI'h nerve palsy. From the Departments of Neurology ( J. W. R., K. B. D., S. G. L.), Ophthalmology ( K. B. D.), and Radiology ( R. H. H.), University of Utah Medical School and the Neurovirology Research Laboratory ( S. G. L.) VA Medical Center, Salt Lake City, Utah, U. S. A. This work was supported by RG 1929- 1- A from the National Multiple Sclerosis Society. S. G. L. was supported by PostDoctoral Fellowship Award FG 796- A- l from the National Multiple Sclerosis Society. K. B. D. was supported by an unrestncted grant to the Department of Ophthalmology from Research to Prevent Blindness. Address correspondence and reprint requests to Dr. John W. Rose, Neurovirology Research Laboratory, VAMC ( 151B), 500 Foothill Dr., Salt Lake City, Utah 84148, U. S. A. 17 Disorders of extraocular motility, especially internuclear ophthalmopelegia and nystagmus, occur frequently in patients with multiple sclerosis ( MS). Dysfunction of the VI'h cranial nerve is much less common. In fact, the appearance of an apparently isolated cranial nerve palsy is considered an unlikely presenting symptom in MS. Similarly, the new onset of such a deficit in a patient with established MS often raises questions about the original diagnosis. It is notable, however, that retrospective studies of patients presenting to the ophthalmologist with the new onset of VIth nerve palsy demonstrate that up to 12% are diagnosed as having MS ( 1- 4). We describe the clinical features of four MS patients with acute dysfunction of cranial nerve VI. Magnetic resonance imaging ( MRI) was able to demonstrate the responsible lesion in three of the four patients. METHODS All images were obtained on a 1.5 Iesla Signa MR scanner ( General Electric, Milwaukee, Wisconsin, U. s. A.). II weighted saggital and axial series were done with a IR of 750 msec and a IE of 20 msec. Axial I2 weighted images were obtained with a IR of 2,800 msec and a IE of 70 msec in patients 1, 2, and 4. Axial images were obtained with a IR of 2,333 msec and a IE of 30 msec in patient 3. All axial images were performed with a 5 mm slice thickness and an interslice gap of 3.5 mm. CLINICAL SUMMARIES Case 1 A 24- year- old white woman developed tinnitus, associated with decreased hearing on the right, but 18 f. W. ROSE ET AL. she did not seek medical attention until 3 weeks later when she had the onset of diplopia. The patient subsequently developed numbness and paraesthesias of the right upper extremity. Neurologic examination revealed a complete left cranial nerve VI palsy, sensorineural hearing deficit on the right, hyperreflexia in the left upper and both lower extremities, and bilateral extensor toe signs. Cerebrospinal fluid ( CSF) protein was 64, and oligoclonal bands were present. The WBC in the CSF was 13/ mm3 with a differential of 97' lr lymphocytes and 3% mononuclear cells. An MRl demonstrated multiple white matter abnormalities in the cerebral hemispheres and a focal area of increased signal intensity in the left pontine tegmentum ( Fig. 1). The patient was treated with a course of prednisone, and the Vlth nerve palsy resolved over 2 weeks. Case 2 A 41- year- old white woman was in good health until she had a reaction to Motrin consisting of fever, headache, and a facial rash. When readministered, the drug led to a recurrence of the reaction with the additional symptom of left hand numbness. These symptoms resolved, and the patient was well until 4 months later, when she developed diplopia. Neurologic examination demonstrated a left VIth nerve palsy and hyperreflexia in the upper extremities. Additional findings included equivo- FIG. 1. T2- weighted axial MR image ( TR/ TE = 2,800 msec/ 70 msec) in patient 1 shows high signal focus ( arrow) In the exact location of the Vlth cranial nerve nucleus. cal Chaddocks signs, past pointing to the left, and decreased perception of vibratory sensation in the lower extremities. A CSF analysis was positive for the presence of oligoclonal bands ( four bands) and markedly elevated IgG synthesis of + 24.1 ( normal range - 5.0 to + 5.0). An MRI revealed multiple areas of increased signal intensity in the white matter and with one focus of increased signal intensity in the left pontine tegmentum extending into the left basis pontis ( Fig. 2). The VI th nerve palsy resolved slowly over a lO- month period. Case 3 A 61- year- old was referred to the neuroophthalmology clinic for evaluation of diplopia, which had developed over several days. During a review of neurologic symptoms, the patient recalled that 3 years earlier, he had a transient diplopia lasting for several days along with progressive lower facial weakness of several years duration. In addition, the patient had experienced stiffness in the right lower extremity for many years. Neurologic examination demonstrated a left VI1h nerve palsy, lower motor neuron distribution right facial weakness, paraparesis with weakness more prominent on the right, right ankle clonus and Babinski sign, and significant loss of vibratory sensation in the lower extremities. A CSF examination revealed the presence of oligoclonal bands ( 4 bands) and a mild elevation of IgG synthesis at FIG. 2. Axial T2- weighted MR ( TR = 2,800 and TE = 70) image in patient 2 reveals multiple high signal foci Within the pontine tegmentum. The dominant lesion ( arrow) is just anterior to the Vlth cranial nerve nucleus. VI'" CRANIAL NERVE DYSFUNCTION 19 5.3 mg/ day ( normal range - 5.0 to + 5.0). A MRI scan demonstrated multiple areas of increased signal intensity in the periventricular white matter, cerebellum, and pontine tegmentum ( Fig. 3). Resolution of the VI1h nerve palsy occurred over a 4- month period. Case 4 A 37- year- old white woman was in excellent health until she awoke with diplopia. The symptom persisted for 1 week before she consulted an ophthalmologist. A left VIth nerve palsy was documented. She had experienced an episode of transient paraesthesias and numbness in the right upper extremity and shoulder, as well as a separate episode in the left lower extremity in the past. Oligoclonal bands ( 5 bands) were demonstrated in the CSF. A MRI scan demonstrated multiple white matter areas of increased signal intensity in the cerebral hemispheres. No pontine abnormalities were detected. The patient was treated with oral prednisone, and the VIth nerve palsy resolved over a 2- week period. RESULTS Three women and one man ranging in ages from 25 to 61 years had VI1h nerve palsy ( Table 1). All patients were found to have abnormal cranial FIG. 3. Axial T2- weighted ( TR = 2,333 and TE = 30) image in patient 3 reveals a high signal focus ( arrow) in the pontine tegmentum involving the fasiculus of the Vl th cranial nerve as it passes anterolaterally to reach the prepontine cistern. MRls demonstrating white matter lesions in both cerebral hemispheres on T2 weighted images. Oligoclonal bands were present in the CSF of all patients at the time of diagnosis. The duration of the VI1h nerve dysfunction ranged from 2 weeks to 10 months. It is interesting that all four patients had a diplopia caused by a VIth nerve deficit as a presenting symptom ( Table 1), which led to further investigation and a diagnosis of MS. All patients had clinical findings in addition to the VI1h nerve palsy; however, signs and symptoms of ipsilateral brainstem injury- facial paresis, Horner's syndrome, conjugate gaze paresis, deafness, loss of taste, and contralateral hemiparesis- were absent. None of the patients had evidence of an internuclear ophthalmoplegia. The patients subsequently experienced periods of relapse and remission and classified as definite MS ( 5). A review of the MRIs revealed that patients 1, 2, and 3 had focal areas of increased signal intensity in the pons ( Figs. 1,2, and 3, respectively). Each of these patients had a white matter abnormality ipsilateral to the side of the palsy as shown by MRI. These focal areas of increased signal intensity involved the VI1h nerve nucleus ( Fig. 1), the pontine tegmentum anterior to the nucleus ( Fig. 2) or the VIth nerve fasciculus ( Fig. 3). In patient 2 the anterior portion of the pons on the opposite side was also abnormal ( Fig. 2). Patients 1 and 3 had areas of increased signal in the cerebellum as well as in the pons. Only patient 4 had no evidence of an infratentorial abnormality by unenhanced MRI ( Table 1). DISCUSSION Many recent studies have documented the sensitivity of the MRI for detection of lesions in MS patients ( 6- 8). Abnormalities of the brainstem tend to correlate with clinical symptomatology and may be demonstrated in 15% of patients at the time of diagnosis ( 8,9). Previous case reports on two individuals suspected of having MS demonstrated pontine lesions on MRI correlating with bilateral gaze palsy. In addition, bilateral fascicular sixth cranial palsies have been documented as individual case reports ( 10,11). The present study indicates that the anatomic site of a lesion producing an apparent VIth nerve palsy in patients with MS can be identified by MRI in some cases. The MRI findings suggest that an acute VIth nerve palsy may be produced by lesions in the tegmentum and/ or the adjacent white matter in the basis pontis. The resultant VI1h nerve palsy JClill Neuro- ophthalmol, Vol. 12, No. 1, 1992 20 f. W. ROSE ET AL. TABLE 1. Multiple sclerosis patients with Vlth cranial nerve dysfunction MRI Findingsb Presenting Patient Age Sex symptom Duration DCS" Cerebrum Cerebellum Pons 1 24 F Yes 2 weeks + + + + 2 41 F Yes 10 months + + + 3 61 M Yes 3 months + + + + 4 37 F Yes 2 weeks + + DCB, oligoclonal bands; MRI, magnetic resonance imaging. " DeS +, Cerebrospinal fluid oligoclonal bands present. . . b MRI +, MRI reveals multiple areas of increased signal intensity in cerebral white matter or focal areas of Increased Signal intensity in the cerebellum or pons as indicated. in these patients was secondary to demyelination of the fasciculus as it courses through the tegmentum or basis pontis. One patient with an acute VI1h nerve palsy had no evidence of involvement near the nucleus of the VI 1h nerve or its fascicle despite an obvious clinical deficit. We have observed a similar situation with definite MS patients presenting with acute onset of either internuclear ophthalmoplegia or IVth nerve palsy. In such cases, the patients with clinical deficits have no evidence of brainstem abnormalities by MRl, but there are obvious lesions distributed in the cerebral hemispheres. Since the unenhanced MRl is dependent on the presence of increased water content to demonstrate an abnormality, the negative result in these patients suggests that brainstem inflammation and demyelination may have been present in small lesions without enough of an increase in water content to be detected by unenhanced MRl. Thus, some acute lesions may have demyelination without increased water content, or they may be small and difficult or impossible to detect by unenhanced MRI utilizing interslice gaps as in patient 4. Time course studies in MS patients with acute onset of VIth nerve palsy would be of particular interest for evaluating the evolution of the brainstem lesions. Future investigation with axial images of reduced thickness without gaps and gadolinium enhancement, which detect defects in the blood brain barrier, will likely increase the sensitivity of MRl for detecting acute brainstem lesions in MS ( 12). REFERENCES 1. Shrader E, Schlezinger N. Neuro- ophthalmologic evaluation of abducens nerve paralysis. Arch Ophthalmol 1960; 63: 108- 15. 2. Rucker C. The causes of paralysis of the third, fourth and sixth cranial nerves. Am JOphthalmol 1966; 61: 1293- 8. 3. Kahana E, Leibowitz U, Alter M. Brainstem and cranial nerve involvement in multiple sclerosis. 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