Neuro-Ophthalmology

Swelling of the extraocular muscles is a common orbital abnormality that is easily demonstrated by computed tomography (CT). However, muscle atrophy is more difficult to identify and is rarely reported in the literature. Bilateral atrophy is extremely rare. We report the CT and clinical features of seven patients showing bilateral extraocular muscle atrophy: four with mitochondrial myopathy (MM) and three with myasthenia gravis (MG). Six patients had clinical histories of muscle involvement >20 years. An incorrect diagnosis of MG was made initially in two patients with MM because of mildly positive Tensilon testing. The ocular motor abnormalities failed to improve after thymectomy in the myasthenic patients. Orbital appearance on neuroimaging is similar in these disorders. Differentiation between these two disorders is impossible with orbital CT and magnetic resonance imaging (MR) alone.

Authors' Abstract, AJO
Niigata University, Japan

Neuro-Ophthalmology

Objective:

To determine the hemodynamic abnormalities that result in visual acuity loss because of retinal or choroidal dysfunction associated with arteriovenous shunts (AVS) that involve the cavernous sinus.

Methods:

Retrospective study of the records of 250 patients with either a carotid cavernous fistula or dural arteriovenous malformation revealed a total of 10 patients with vision loss secondary to retinopathy (group I) or choroidal effusion (group II). The cerebral angiograms of these 10 patients and 10 additional patients with visual dysfunction due to elevated intraocular pressure (group III) were evaluated to determine whether the three groups could be distinguished by a specific vasculopathic pattern. Particular attention was given to the extent of thrombosis in the ophthalmic venous system and cavernous sinus.

Results:

There were angiographic signs of severe thrombosis in the ophthalmic vein in nine patients and in the cavernous sinus in seven patients ipsilateral to the retinal or choroidal lesion. In contrast, in group III, severe thrombosis in the ipsilateral ophthalmic vein and in the cavernous sinus occurred in one and two patients, respectively. Closure of the AVS improved the visual acuity in 1 of 4 patients in group I and in 4 of 5 patients in group II, and normalized the intraocular pressure in all patients.

Conclusions:

Ophthalmic vein thrombosis, rather than arterialization of the venous system or an arterial ''steal,'' is the principal cause of retinal or choroidal dysfunction associated with AVS to the cavernous sinus. Following AVS closure, visual recovery is more frequent with choroidal effusion or detachment rather than with retinopathy.

Authors' abstract, JNO
NYU, NY, NY

Neuro-Ophthalmology

Various mutations in the mitochondrial tRNA(Leu(UUR)) gene give rise to a variety of neurological disorders. Among these, mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS syndrome) are frequently associated with a tRNA(Leu(UUR)) mutation at nucleotide position 3243 of the mitochondrial DNA. A supplementary clinical feature seen in these patients is headache in early life. Recently, a tRNA(Leu(UUR)) mutation at nucleotide position 3243 has been found in a patient presenting with cluster headache. This led us to examine the mitochondrial genomes of 22 patients presenting with cluster headache. None of the patients harboured the reported tRNA(Leu(UUR)) mutation or any other length variations of the mtDNA. Cluster headache is most likely not causally associated with the A3243G mutation of the mitochondrial DNA. [References: 14]

Author's abstract, J Neuro
Dresden, Germany