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Anti GQ1b antibody disorders

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The anti-GQ1b antibody is often associated with acute paresis of the ocular muscles. Thus it is an autoimmune disorder that causes eye muscle weakness. This antibody interacts with the peripheral nerve ganglioside is the one that interacts with the peripheral nerve ganglioside, Gq1b. G1qb is expressed at neuromuscular junctions, sensory nerves, and proximal segments of crainal nerves.

The antibody has been found in:

Acute ophthalmoplegia without ataxia (AO)

AO is a rare disorder considered to be a variant of GB (see below). The most common manifestation of AO is external ophthalmoplegia with bilateral abduction deficits followed by involvement of the 3rd nerve and internal opthalmoplegia (pupillary paralysis). It should be distinguished from other causes of eye muscle weakness including cerebrovascular disease, tumors, infections, diabetes, multiple sclerosis, and myasthenia gravis. Detection of the anti-GQ1b antibody is useful in that it makes the other possibilities much less likely.

A movie of a patient who has ophthalmoplegia (although not this particular syndrome) is found here. Note that while the head moves, the eyes are locked in place.

AO is treated with plasmaphereis and IVIG.

Bickerstaff's brainstem encephalitis. (BBE)

Bickerstaff's encephalitis is a rare condition first described in the 1950's by Bickerstaff and Clark. They noted the combination of ophthalmoplegia, ataxia, and altered sensorium. They commented on the similarity to the Guillain-Barre syndrome, as well as the high protein with normal cells in the spinal fluid. BBE is more common in Japan than the USA. In Japan, the estimated annual incidence is estimated at very low -- about 0.078 in 100K. The altered sensorium is the feature that distinguishes BBE from MFS (see below), and coma occurs in as many as 1/5. MRI may show high T2.

There have been no treatment studies as of 2013. Attempts have been made to treat with plasmapheresis, IVIG, and Rituxin.

Guillain-Barre syndrome (GB)

This is a rare ascending neuropathy characterized by weakness and areflexia. Again, there is high protein with normal cells in the spinal fluid. These patients do not have a disorder of their eye movements, but may become paralyzed. Reflexes are typically absent. There may be dysautonomia.

Some of these patients have had a previous infection with a URI, and there is an increased seropositivity to both Campylobacter Jejuni and Haemophilus influenzae. GBS is thought to have an incidence of about 1.11 cases/100K patient years.

Treatment is similar to AO and BBE. Some patients need respiratory support.

Miller-Fisher Syndrome (MFS)

This is a rare disorder related to Guillain Barre, and often categorized as a GB variant. MFS is characterized by a combination of ataxia, weakness or paralysis of the eye movements, and peripheral neuropathy with areflexia. Unlike Bickerstaff's, these patients do not have any alteration in their thinking. Most patients present with diplopia and eventually develop complete paralysis of their eyes. Internal ophthalmoplegia (pupillary paralysis) occurs in about 40% of patients. Antibodies to the ganglioside GQ1b are often associated with Miller Fisher syndrome. This condition should be considered when there is a combination of diplopia, ataxia, and loss of deep tendon reflexes. The ataxia is probably due to loss of sensory input to the cerebellum. Mean time of recovery is at 10 weeks. About 1-5% of GB cases are categorized as MFS. MRI is typically normal.

Treatment is similar to AO and BBE.

References:

 

Copyright December 14, 2014 , Timothy C. Hain, M.D. All rights reserved. Last saved on December 14, 2014