Neuromuscular disorders Flashcards
What is Lambert-Eaton syndrome?
Caused by antibodies to the P/Q-type voltage gated calcium channels (at axon terminals). Causes fatigable proximal muscle weakness, ocular and bulbar involvement is rare (as opposed to myasthenia gravis), with prominent autonomic symptoms. Often associated with small cell lung cancer
What does symmetric proximal weakness suggest?
Primary muscle problem. Weakness of neck flexors and extensors also suggests this
What percentage of cases of dermatomyositis are associated with an underlying neoplasm?
15% of cases are associated with neoplasm - lungs, ovaries, GI tract, breasts, and other organs
What neurons are affected in spinal muscular atrophies (SMAs)?
Alpha motor neurons leading to wasting, fasciculations and weakness with spasticity
What is Werdnig-Hoffmann disease?
An SMA presenting in infancy
What is limb-girdle muscular dystrophy?
Due to mutation to the sarcoglycan or other structural proteins (e.g. calpain, caveolin). Proximal muscle weakness occurs, but there is no ocular or bulbar involvement
What are the main features of myotonic dystrophy?
Caused by a CTG expansion in the DMPK gene. Characterized by distal muscle weakness initially (most other muscular dystrophies by contrast begin with proximal muscle weakness). It is generally adult onset. It is also associated with cataracts, ptosis, arrhythmias, dysphagia, insulin resistance, testicular atrophy, and frontal balding. Can have neurobehavioral changes. CK levels are typically normal or only mildly elevated
What is Emery-Dreifuss muscular dystrophy?
Caused by mutations in the emerin gene on the X chromosome. Characterized by joint contractures and a slowly progressive humeroperoneal pattern of weakness (early involvement of biceps, triceps, peroneal, and tibial muscles) and atrophy, and a cardiomyopathy. Female carriers are at risk for cardiac complications
What is Werdnig-Hoffmann and Kugelberg-Welander disease?
Both are spinal muscular atrophies (congenital motor neuron disease). The former is especially lethal and the child’s life expectancy is weeks to months (presents with congenital weakness, hypotonia, and muscle atrophy). A similar pattern of weakness occurs in older children with Kugelberg-Welander disease
What is the intellectual function of children with Duchenne muscular dystrophy?
Slightly impaired
What is the EMG pattern seen in the muscles of patients affected by myotonic dystrophy?
Repetitive discharges with minor stimulation (“dive bomber pattern”)
What is polymyalgia rheumatica?
It is a syndrome with pain or stiffness, usually in the neck, shoulders, upper arms, and hips, but which may occur all over the body. It is an arteritis of the elderly (very improbable in someone under 60). There is often a normal CPK level
What is the EMG pattern seen with anterior horn cell damage (e.g. ALS)?
Fibrillations
What are F wave on EMG?
F waves are often used to measure nerve conduction velocity, and are particularly useful for evaluating conduction problems in the proximal region of nerves (i.e., portions of nerves near the spinal cord). Prolonged or absent F waves may be seen in demyelinating disorders such as Guillain-Barré.
