Procedure
To investigate the strength of a muscle, have the patient tense and contract the muscle maximally. Subsequently try to overcome the resistance exerted by the patient using your arm and/or hand muscles. When assessing the patient’s strength, take into consideration your own physical build compared to that of the patient. During the examination of the normal movement pattern, you will have gained an impression of any loss of strength that may be present. You will gain greater insight into the situation if you examine the muscles individually wherever possible. Try to score the strength of each muscle (group) semi-quantitatively on a scale of 0-5, and always compare left and right.
0 No movement possible, muscle tension cannot be felt.
1 The muscle is visibly tensed, movement is not possible.
2 Movement is possible in a situation where gravity is reduced or absent
(e.g., movement under water).
3 The muscle strength is sufficient to overcome gravity.
4 The resistance produced by the patient is slightly less than you would expect
given the patient’s physical build.
5 The resistance exerted by the patient is normal.
Interpretation
If you observe loss of strength, you should ask yourself whether this is due to a muscle disease, a peripheral nerve disorder or a condition involving the corticospinal pathway. If the loss of strength is accompanied by hyper reflexes and/or spasticity on the affected side, a central lesion is probable. If the loss of strength is accompanied by hypotonia, sensory loss and impaired reflexes on the affected side (decreased or absent reflexes), a peripheral nerve lesion is likely. A condition involving the motor neurons is characterised by loss of tone, loss of strength, decreased or absent reflexes, but no sensory loss; fasciculations are often present as well. A muscle or neuromuscular junction condition is also associated with loss of tone, loss of strength and decreased or absent reflexes, but is usually symmetrical and located in more proximal muscle groups.