Miller Fisher syndrome is even rarer than Guillain-Barré syndrome. Despite the similar pathologic mechanisms of these two conditions, the clinical presentations differ drastically. Whereas Guillain-Barré syndrome typically presents with an ascending paralysis, Miller Fisher syndrome usually presents with involvement of the lower facial and cranial nerves and, in most cases, with at least two of the following features:
Ophthalmoplegia and ptosis
This patient's presenting symptoms suggested the diagnosis of Miller Fisher syndrome, which was confirmed with serologic testing of the cerebrospinal fluid.
CMT disease, also known as "hereditary motor and sensory neuropathy," is another disorder that involves damage to peripheral nerves. CMT disease is genetically inherited via an autosomal dominant, autosomal recessive, or X-linked pattern. A duplication of the PMP22 gene on chromosome 17 leads to abnormal function of the proteins that regulate the structure and function of the peripheral nerve axon or myelin sheath of both motor and sensory nerves. The nerves slowly degenerate, causing typical symptoms of lower motor neuron lesions, such as atrophy, weakness, and hyporeflexia. Foot deformities are the distinguishing feature of CMT disease. Pes cavus and hammer toes are pathognomonic of this disorder, and the diagnosis can usually be made by means of a detailed history and physical examination findings. If further confirmation is needed, electromyography can be performed to detect signs of axonal loss.
Because no definitive interventions exist, treatment is mainly supportive. Occupational therapy and orthopedic devices can help restore quality of life as well as improve activities of daily living. Physical examination of the patient in this case revealed no structural abnormalities of the feet. This finding, in addition to the associated lack of a family history of CMT, excluded this disease as the cause of the patient's symptoms.
Myasthenia gravis was considered in the differential diagnosis owing to the patient's ocular findings. This autoimmune neuromuscular disorder is characterized by weakness in the skeletal muscles that progresses and worsens over time. The annual incidence is thought to be between 0.25 and 20 per 1,000,000 population, and the mortality rate is very low (less than 1 per 1,000,000 population). The most common presenting symptoms of myasthenia gravis are double vision, muscle weakness, fatigue, and difficulty in speaking. The anti–acetylcholine receptor (AChR) antibody test is highly specific (up to 100%) for the diagnosis of autoimmune myasthenia gravis. The AChR antibody was not found in this patient's blood titers. Furthermore, with the exception of double vision, the patient had none of the classic symptoms of myasthenia gravis.
Another condition that was considered in the differential diagnosis in this case was intoxication with the botulinum toxin, produced by the bacterium C botulinum. Adults typically ingest the preformed toxin in canned foods, whereas infants are more likely to ingest the spores of the toxin through consumption of such foods as honey. The toxin exerts its effects by binding and preventing the release of acetylcholine from the presynaptic neuron in the peripheral nervous system, leading to flaccid paralysis. Only about 110 cases of botulism are reported in the United States each year. Botulinum toxicity was ruled out in this patient, owing to the presence of central nervous system symptoms as well as an absence of a history of ingestion of canned foods.
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Cite this: Sujatha R. Borra, Rahul R. Borra, Darshan Rola, et. al. A 47-Year-Old With Diplopia, Limb Tingling, and Imbalance - Medscape - Aug 03, 2021.