How can alterations in deep tendon reflexes aid in differentiation of neuromuscular diseases?
• Spinal cord lesions (above L1 to L2) and upper motor neuron disease usually produce exaggerated deep tendon reflexes and pathologic extensor plantar reflexes. Of note, acute spinal cord lesions can occasionally lead to depressed or absent reflexes initially (i.e., spinal shock).
• Nerve root and peripheral nerve lesions usually produce depressed or absent reflexes. Small fiber neuropathies often have normal reflexes.
• Primary muscle diseases do not usually present with altered deep tendon reflexes. Late in the disease process, however, substantial muscle atrophy may cause reduction or loss of the reflex.
• Hyperthyroidism produces exaggerated tendon reflexes.
• Hypothyroidism produces depressed deep tendon reflexes with slow relaxation phase.
• Many people aged over 60 years experience a natural loss of their ankle reflexes.