Evaluation of a patient with weakness Flashcards
What are the levels of the nervous system that can produce true weakness?
- Upper motor neurons (descending tracts of the central nervous system)
- Lower motor neurons (the anterior horn cell and the axons traveling through the peripheral nerve to the muscle)
- The neuromuscular junction
- The muscle.
How is strength graded?
A 5 point scale:
- 5 being normal
- 4 being weak
- 3 being only strong enough to move against gravity and no additional resistance
- 2 being unable to move against gravity
- 1 being a flicker of contraction of the muscle, but no actual limb movement of any kind.
How can strength be tested functionally?
- The patient can attempt to hold the arms out in front, with weakness of the whole upper limb reflecting in pronator drift.
- Grip can be tested by squeezing of two of the examiner’s fingers.
- Making an “OK” sign with the thumb and index finger tests the thenar muscles.
- Abduction and adduction of the ulnar 4 digits tests interosseous and hypothenar muscles.
- Walking on the toes and heels, climbing a small step, hopping on one foot or rising from a chair tests lower extremity muscles.
Other than actual weakness, what other symptoms might the patient be describing when they use the term “weak”?
- Rigidity
- Incoordination
What is suggested by proximal, symmetrical distribution of weakness (hip and shoulder girdle)?
This is the pattern most often seen in a myopathic process.
What is suggested by distal, symmetrical distribution of weakness (feet and/or hands)?
This is the pattern most often seen in a neuropathic process.
What does it mean if the atrophy is out of proportion to the degree of disuse?
This indicates lower motor neuron lesion.
What would be suggested by fatigability of muscles?
Neuromuscular diseases, such as myasthenia gravis, can produce fatigue of muscles.
What conditions can cause transient weakness?
- Transient ischemic attacks
- Neuromuscular diseases (like myasthenia)
- Peripheral nerve entrapment problems
- Periodic paralysis family of conditions
- Migraine can cause transient weakness.
- Patients can also be transiently weak after a seizure (Todd paralysis).
What is suggested by a story of severe, global weakness associated with heavy meals or periods of exercise?
This is a story suggestive of one of the periodic paralyses (an ion channelopathy).
- There may be a family history of similar problems.
What systemic conditions can produce weakness?
- Thyroid or adrenal dysfunction
- Certain rheumatologic/inflammatory conditions can lead to muscle damage (myopathy).
- Diabetes mellitus, hypertension, dyslipidemas predispose to cerebrovascular disease
- Can damage upper motor neurons.
How can pain affect the diagnosis of the patient with weakness?
- Pain may be part of the condition (particularly those that damage nerves or muscle).
- Pain may also produce an unwillingness or even inability to use the body part.
What conditions can present as bilateral weakness of the lower limbs?
- Myelopathy (damage or disease of the spinal cord) usually produces bilateral symptoms below a certain level, often with some bladder urgency (this may require urgent MRI scanning of the cord).
- Cauda equina compression (syndrome) is suggested by flaccid weakness of the legs, often with urinary retention or overflow incontinence.
- Guillain - Barre => progressive weakness of both legs, evolving over hours to days
- Myopathic processes tend to affect the hip girdle muscles early
- Lambert-Eaton myasthenic syndrome usually begins with proximal hip girdle muscle weakness.
What is the likely cause of weakness of one side of the body that is associated with a lower facial weakness on the same side?
The problem is with upper motor neurons above the level of the brainstem
- Usually cerebral cortex or internal capsule.
What is the likely cause of weakness of one side of the body that is associated with weakness on the opposite side of the head (tongue, jaw, palate or eyes)?
The damage is localized to the brain stem (usually the medial aspect).
