Neurosciences News

  Jeffrey Chang Vivek Chaturvedi A 27-year-old woman was referred to the New England Eye Center for evaluation of bilateral restricted eye movements, for which the patient characterized as being “in a daze.” She had initially presented to an outside hospital approximately 1 year prior after a syncopal episode characterized by weakness, nausea and vomiting. She recalled that she would often fall over to the right and had extreme dizziness. On further questioning, she reported difficulty with slurred speech, hiccups, tinnitus and dysphagia to both solids and liquids. She denied seizures, headaches, and gastrointestinal or genitourinary complaints. Initial workup revealed an enhancing lesion in the left medulla and cerebellar peduncle (Figure 1). A lumbar puncture was nondiagnostic, and she was started on Keppra (levetiracetam, UCB) and Decadron (dexamethasone, Merck). Over the course of the year, however, she developed progressively worse diplopia with lateral gaze. She also noticed that while watching television, the images would shake. The patient’s ocular history was unremarkable. Her medical history was significant for aspiration pneumonia after intubation, which was done as a precaution due to her dysphagia. She was not taking any medications and reported no family history of ophthalmic problems. She had an allergic reaction to Keppra, in which she developed pancreatitis. She denied smoking, drinking and illicit drug use. Examination On examination, the patient’s visual acuities were 20/25 in both eyes without correction. There was no afferent pupillary defect. IOP, color vision, Hertel measurements, eyelids and orbits were all within normal limits. The most salient feature on exam was a bilateral horizontal gaze palsy (Figure 2); horizontal gaze was limited with both saccadic and pursuit attempts. Note that convergence produced greater medial rectus excursions than attempted horizontal gaze. Vertical gaze was intact, but associated with some downbeat nystagmus. The patient was unable to tolerate optokinetic drum testing. Maddox rod testing revealed a relatively comitant, small 1 ΔD to 3 ΔD left hypertropia (Figure 3). Her anterior and posterior slit lamp examinations were unremarkable except for tilted discs in both eyes. There was no disc edema. Neurological examination was significant for intact facial sensation and orbicularis oculi strength, but slightly weakened nasolabial folds symmetrically. Hearing was normal. The tongue and uvula were midline. Shoulder strength was normal. MRI at the time of consultation showed that the brainstem lesion had progressed from the medulla to the tectum of the pons and now involved the superior and middle peduncle (Figure 4). Initial MRI shows high T2 signal involving the central and left medulla, as well as the left inferior cerebellar peduncle. There is no enhancement and no meningeal lesions; the ventricles, sulci and blood vessels are normal. Images: Landmann DS, Hedges TRNotice the bilateral horizontal gaze palsy with full ductions in the vertical directions. The patient, converging on a pen at near.MRI 1 year later. Gadolinium images show the lesion now extends to the poster aspect of the pons immediately inferior to the caliculi and anterior to the fourth ventricle as well as the middle and superior cerebellar peduncle. What is your diagnosis? Bilateral horizontal gaze palsy The differential for this case can be constructed on the basis of the disease progression and the radiological appearance. Based on the patient’s age, sex and progression, one must consider a demyelinating process; however, the lack of periventricular lesions and the negative lumbar puncture do not support this hypothesis. On the basis of the MRI findings, the presentation is consistent with a glioma or astrocytoma. The patient had been in contact with someone with tuberculosis, so this should also be considered. Sarcoidosis is also a possibility, given the patient’s age and gender. Although this patient was not taking any medicines, carbamazepine and various tricyclic antidepressants have been known to cause gaze palsies, although none have been found to cause such severe bilateral gaze palsies as in our patient. Möbius syndrome is a congenital disorder, and the symptoms would have presented earlier in the patient’s life. Duane’s retraction syndrome is not associated the observed radiologic findings nor the other symptoms such as syncope and dysphagia. Diagnosis Several weeks after her initial appointment in the neuro-ophthalmology clinic, the patient’s condition rapidly declined. She had worsening of her bilateral gaze palsy and lower face weakness as well as dysphagia, which made breathing more difficult with frequent aspirations. She was admitted to the intensive care unit for close monitoring of her breathing. Repeat cerebrospinal fluid analysis was again nondiagnostic, although cytomegalovirus was detected. The cerebrospinal fluid was clear, lymphocytes were elevated (95), monocytes and macrophages were low (5), and protein and glucose levels were normal. There were no oligoclonal bands, and myelin basic protein was not detected. Cerebrospinal fluid was also tested for but did not reveal herpes simplex virus types 1 or 2, Epstein-Barr virus, varicella-zoster virus, JC virus, Mycobacterium tuberculosis, toxoplasmosis, human T-cell lymphotropic virus types 1 or 2, HIV, cryptococcal Ag, syphilis, Lyme, hepatitis B, hepatitis C or ACE. The patient underwent a suboccipital craniotomy and a biopsy of the left middle cerebellar peduncle. A pathological diagnosis of demyelination was made on the basis of Luxol blue and C68 staining. Discussion Horizontal gaze is controlled primarily by the abducens nuclei and the parapontine reticular formation. The paramedian pontine reticular formation, located near the abducens nuclei, is involved in the generation of ipsilateral horizontal saccades. Lesions of the abducens nerve, also known as the horizontal gaze center, cause an ipsilateral gaze palsy in both eyes. The clinical presentation, laboratory results including lumbar puncture and MRI data in this case were inconclusive. Typically, MRI findings of demyelinating lesions on T1 imaging will show active lesions that are 2 weeks old to 6 weeks old. This reflects perivascular inflammation and breakdown of the blood-brain barrier. Older demyelinating lesions are seen on T2 imaging as periventricular supratentorial white matter changes. These findings, however, are nonspecific for both inflammation and infection. MRI imaging of gliomas is characterized by decreased signal relative to the surrounding brain on T1 weighted images, whereas on T2 images, a higher signal reflects both the tumor and surrounding edema. Bilateral horizontal gaze palsies with preserved vertical gaze is a rare disorder. As a separate entity, it has been described in Möbius syndrome, congenital agenesis of the seventh and sometimes sixth cranial nerves. There are scattered case reports in the literature that describe similar findings secondary to pontine infarction, hemorrhage, glioma and metastases. Also, cerebellar abscess and multiple sclerosis have been described to cause similar findings. This case describes a young woman with a brainstem lesion that was initially located in the medulla, but progressed to the tectum of the pons. Because of her symptomatic progression and MRI changes, the primary concern was that a glioma was responsible. The final pathological diagnosis of demyelination supports the old adage that “common things are common.” This is an unusual presentation of demyelination in an area of mostly nuclear structures resulting in bilateral horizontal gaze palsy. For more information: Dan S. Landmann, MD, and Thomas R. Hedges III, MD, can be reached at New England Eye Center, Tufts University School of Medicine, 750 Washington St., Box 450, Boston, MA 02111; 617-636-4219; fax: 617-636-4866; Web site: www.neec.com. Edited by Jeffrey Chang, MD, and Vivek Chaturvedi, MD. Drs. Chang and Chaturvedi can be reached at New England Eye Center, Tufts University School of Medicine, 750 Washington St., Box 450, Boston, MA 02111; 617-636-4219; fax: 617-636-4866; Web site: www.neec.com. Drs. Chang and Chaturvedi have no direct financial interest in the products mentioned in this article, nor are they paid consultants for any companies mentioned. References: Miller NR, Newman NJ, Biousse V, Kerrison JB. Walsh & Hoyt’s Clinical Neuro-Ophthalmology: The Essentials. 2nd ed. Lippincott Williams & Wilkins; 2007. Spector RH, Stark S. Peripheral facial palsy with intact taste and tearing caused by intrapontine lesion. Arch Neurol. 1983;40(5):317-319. Tan E, Kansu T. Bilateral horizontal gaze palsy in multiple sclerosis. J Clin Neuroophthalmol. 1990;10(2):124-126.

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