ALS Flashcards
Amyotrophic Lateral Sclerosis (ALS) is also called…
Lou Gehrig’s Disease
ALS LMN
Lesion sites:
-anterior horn cells (alpha & -gamma motor neurons (LMN signs)
Starts distal and works proximally –hands and feet are effected first and atrophies
ALS UMN
Lesion sites:
- lateral corticospinal tract
- motor nuclei of brainstem
- motor area of frontal lobe (UMN signs)
-rarely any sensory involvement in ALS
Primary pathologic defect…
- is in the motor neuron cell body (specific to anterior horn cell in the spinal cord)
- motor cells in the brainstem motor nuclei (cranial nerves)
- pyramidal cells in the primary motor cortex thus loss of the upper motor neurons in corticospinal tracts (Betz cells)
Cause of the neuropathology associated with ALS
- unknown at this time
- Possible causes include: Mitochondria
- Currently, the most prevalent theory is that a SOD1 gene mutation causes the superoxide dismutase (SOD) enzyme to function improperly.
SOD1 gene mutation
- causes the superoxide dismutase (SOD) enzyme to function improperly.
- SOD enzyme is a strong anti-oxidant that the mitochondria need to perform their respiratory function
- The respiratory and ATP function is compromised and the nerve cell begins to atrophy.
Other possible causes are…
- Glutamate: elevated in the cerebrospinal fluid and blood in ALS patients up to concentrations that could be neurotoxic. Over-excitation of glutamate-sensitive cells in the nervous system may result in their premature degeneration and death.
- Exogenous toxins
- Viral disease
- Immunologic disturbances
ALS Stats
- 0.1% of adult deaths in U.S.
- ALS is a disease of late middle life and is rarely seen prior to age 40.
- 90% of all cases begin between the ages of 40 and 70 years
- some predominance in men (estimated at 1.5-2.0 males to 1 females)
Signs & Symptoms
- First sign is usually asymmetric, distal weakness (e.g. difficulty in manipulating objects with the fingers or dragging one leg during walking)
- When pt’s complain of weakness, they often have lost 80% of their alpha MN in the areas of weakness
- Progress to mm atrophy and severe mm weakness
- CN cell atropy
- Control of bladder, bowel, and autonomic function is largely unimpaired, however, some studies report sub-clinical involvement
Early Signs
Severe muscle cramps and/or fasciculations at rest
EMG
- Spontaneous fibrillations
- Fasciclations with giant unit spikes upon voluntary activity
Progress to muscle atrophy and severe muscle weakness
- decrease # of muscle fibers
- type II fibers tend to atrophy earlier and more rapidly than type I fibers
Cranial nerve cell atrophy leads to
- Dysarthria
- Dysphagia
- difficulty in chewing
- tongue weakness
- Fasciculations may be prominent
- Hypoglossal, facial, and trigeminal nuclei are most severely involved
Motor and Sensory Signs
- Motor signs and symptoms only
- NOT sensory - sensory systems or the special senses are rarely involved (this is primarily a motor neuron cell body disease), however, pain and paresthesia are often reported
LMN signs
- Progressive muscle atrophy
- Weakness (asymmetric weakness is often a presenting sign)
- Fasciculations (especially -evident in tongue, deltoid)
- Muscle cramps (painful)
