caused by a nerve toxin that is produced by the bacterium Clostridium botulinum. Botulism toxin interferes specifically with the release of acetylcholine so the nerve cannot stimulate the muscle to contract.
The classic symptoms of botulism include double vision, blurred vision, drooping eyelids, slurred speech, difficulty swallowing, dry mouth, and muscle weakness. Infants with botulism appear lethargic, feed poorly, are constipated, and have a weak cry and poor muscle tone.
Clinically, botulism neurotoxin is the active ingredient of Botox. Unless the nerve can regenerate a new axon that has no exposure to the neurotoxin, the interference at the neuromuscular junction is permanent. This is why it takes so long (weeks to months) to recover from botulism and also why cosmetic and therapeutic uses of diluted neurotoxin can be effective for relatively lengthy time periods.
Symptoms, which vary in type and severity, may include asymmetrical ptosis (a drooping of one or both eyelids), diplopia (double vision) due to weakness of the muscles that control eye movements, unstable or waddling gait, weakness in arms, hands, fingers, legs, and neck, a change in facial expression, dysphagia (difficulty in swallowing), shortness of breath and dysarthria (impaired speech, often nasal due to weakness of the pharyngeal muscles). In myasthenic crisis a paralysis of the respiratory muscles occurs, necessitating assisted ventilation to sustain life. is a hereditary disease characterized by progressive hypotonia and paresis due to alpha motor neuron degeneration.
Weakness is more severe in proximal musculature than in distal segments.
LMN signs can include tongue fasciculations (a common sign) and atrophy of muscles innervated by CN XII.
Sensation, which originates from the posterior horn cells of the spinal cord, is spared, as is intelligence.
Several muscles are spared, including the diaphragm, the involuntary muscles of the gastrointestinal system, the heart, and the sphincters.
A common cold can easily turn into pneumonia which is what usually takes the lives of these children, along with "respiratory failure" or when they no longer have the lung or chest muscles to be able to breathe on their own.
Current statistics show that the average lifespan of a child with SMA Type I (most severe), not put on permanent ventilation or "life support", is only 8 months of age, with 80% dying by the age of one, and the majority of the rest dying by age 2.
Incurable autosomal recessive disease caused by a genetic defect in the SMN1 (survival motor neuron) gene, necessary for motor neuron survival.