Facial onset sensory and motor neuronopathy

Alternate names

Facial onset sensorimotor neuronopathy syndrome; FOSMN syndrome; Facial onset sensory and motor neuronopathy syndrome

Definition

Facial onset sensory and motor neuronopathy (FOSMN) is a rare and slowly progressive motor neuron disorder.

Cause

• The underlying cause of facial onset sensory and motor neuronopathy (FOSMN) is currently unknown.
• Because the clinical features and severity of the condition can vary significantly from person to person, it is thought that there may be a multifactorial cause.
• Some studies suggest that the condition may occur due to an abnormal immune response or neurodegeneration (degeneration of certain motor and sensory neurons, specifically).
• Studies have also shown that SOD1 and OPMD genes may play a role in FOSMN; however, the specific association is unclear.
• Although there are currently no familial cases of FOSMN reported in the medical literature, some scientists suspect that newer genetic testing technologies may uncover additional genetic factors.

Inheritance

• There is currently no evidence to suggest that facial onset sensory and motor neuronopathy is inherited.
• To date, no familial cases have been reported which means that the condition appears to occur sporadically in people with no family history of the condition.

Signs and symptoms

• Signs and symptoms of facial onset sensory and motor neuronopathy (FOSMN) generally become apparent by age 54 (range 38-77 years) and vary significantly from person to person.
• The earliest symptoms include facial tingling and numbness which eventually spread to the scalp, neck, upper trunk and upper limbs.
• These sensory abnormalities often present months to years prior to the development of motor symptoms such as cramps, muscle twitches, difficulty swallowing, dysarthria, muscle weakness and atrophy.
• The hallmark of FOSMN is the reduced or absence of the corneal reflex (the reflex to blink when something touches the eye).

For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. 80%-99% of people have these symptoms

• Dysarthria(Difficulty articulating speech)
• Dysphagia(Poor swallowing)
• Fasciculations(Muscle twitch)
• Muscle spasm
• Muscle weakness(Muscular weakness)
• Paresthesia(Pins and needles feeling)
• Skeletal muscle atrophy(Muscle degeneration)

Diagnosis

Due to the small number of reported cases, there are no agreed upon diagnostic criteria for facial onset sensory and motor neuronopathy. A diagnosis is often suspected based on the presence of characteristic signs and symptoms. Additional tests may then be ordered to support the diagnosis and rule out other conditions that are associated with similar features. These include:

• Electromyography and nerve conduction studies
• Laboratory tests
• Lumbar puncture (spinal tap)
• MRI of the brain and spinal cord

Treatment

• Due to the rarity of the condition, the best approach for effective treatment is currently unclear.
• Several treatments have been mentioned in case reports including intravenous immunoglobulin (IVIG), plasmapheresis (PE), corticosteroids, azathioprine, mycophenolate mofetil, and rituximab.
• Although some patients showed temporary improvements with IVIG and PE, the majority of cases did not respond to any of these treatments.

NIH genetic and rare disease info

• NIH info on Facial onset sensory and motor neuronopathy

Facial onset sensory and motor neuronopathy is a rare disease.

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