Chapter 8 - Reflex evaluation

Questions

Define the following terms:

hyper-reflexia, pathological spread of reflex, clonus, Babinski sign, Hoffmann's sign, myotatic reflex, upper motor neurons, lower motor neurons, reinforcement.
Hyper-reflexia is excessively brisk reflexes
Pathological spread of reflex occurs when a reflex contraction occurs in a muscle whose tendon was not stretched (i.e., finger flexion when testing the brachioradialis reflex or thigh adduction when the patellar reflex is tested). It is a suggestion of hyperactive reflexes.
Clonus is repeated contraction of muscles (usually the calf muscles or the wrist flexor muscles) when the muscles are stretched manually (such as by ankle dorsiflexion or wrist extension). Sustained clonus is when this occurs repeatedly as long as the stretch is maintained.
Babinski sign is reflex dorsiflexion of the great toes and fanning of the other toes by stroking the lateral side of the sole of the foot. This stroke is often continued across the ball of the foot toward the base of the great toe. This occurs in patients with upper motor neuron damage. The normal plantar response is for the great toe to flex.
Hoffmann's sign is flexion of the thumb following a maneuver that consists first of passive flexion of the patient's middle finger by pressure over the nail bed, followed by sudden release of this pressure. It is a sign of brisk reflexes but is not pathological unless it is accompanied by other signs of upper motor neuron damage or is asymmetrical.
Myotatic reflex is the muscle stretch reflex (often termed the deep tendon reflex).
Upper motor neurons are the principal descending motor pathways for voluntary movement, including the corticospinal and corticobulbar tracts (and some other associated tracts).
Lower motor neurons are the anterior horn motor neurons and their axons that extend through the ventral nerve root and the peripheral nerves to reach the neuromuscular junction.
Reinforcement involves the strong contraction of muscles outside of the area in which muscle stretch reflexes are being tested. This will serve to increase the reflexes. Specific examples include clenching the jaw, pressing the feet together or clasping the hands and attempting to pull them apart (the Jendrasik maneuver).

8-1. What is the main effect of descending motor systems on reflexes?

Answer 8-1. Motor cortex and descending motor pathways are generally involved in suppressing (inhibiting) reflexes.

8-2. What are the 7 Deep Tendon Reflex exams (DTRs)? What sensory/motor nerves are they testing?

Answer 8-2. Biceps - musculocutaneous nerve and mainly C6; Triceps - radial nerve and mainly C7; Brachioradialis (radial periosteal) - radial nerve and mainly C6; Finger flexor - musculocutaneous nerve and mainly C7-8; Patellar - femoral nerve and mainly L3-L4; Achilles' reflex (ankle jerk) - tibial nerve and mainly S1; Jaw jerk - trigeminal

8-3. What are the superficial reflexes?

Answer 8-3. Superficial reflexes include: abdominal, cremaster, plantar, anal wink.

8-4. What is the effect of damage to corticospinal fibers on myotatic (deep tendon) reflexes? What is the effect on superficial reflexes?

Answer 8-4. DTRs increase with damage to descending motor pathways; superficial reflexes decrease with damage to descending motor pathways.

8-5. What primitive reflexes emerge with diffuse bilateral hemispheric dysfunction?

Answer 8-5. Diffuse bilateral hemispheric dysfunction can dysinhibit grasp, glabellar, suck, rooting, oculocephalic and nuchocephalic reflexes.

8-6. What happens to DTRs with lesions in the cerebellum & basal ganglia?

Answer 8-6. Usually no change, though may be sluggish with cerebellar damage.

8-7. How are DTRs graded?

Answer 8-7. 0-4+. To grade a reflex as "0", you must try reinforcement. 4+ means there is sustained clonus. 1 is sluggish, 2 is "normal" and 3 is "brisk".

8-8. What is the most important consideration in testing reflexes?

Answer 8-8. Symmetry.

8-9. What reflex changes would occur in lesions of muscles?

Answer 8-9. No change unless end stage.

8-10. What reflex changes would occur in lesions of the neuromuscular junction?

Answer 8-10. Normal to decreased depending on severity of weakness.

8-11. What reflex changes would occur in lesions of the peripheral nerves?

Answer 8-11. Decreased in clinically affected areas.

8-12. What reflex changes would occur in lesions of the nerve root?

Answer 8-12. Decreased in clinically affected areas.

8-13. What reflex changes would occur in lesions of the spinal cord and brain stem?

Answer 8-13. Usually reflexes will be increased unless the gray matter (anterior horn cells, lower motor neurons) is damaged right at the reflex level. Acute spinal cord injury can result in spinal cord shock (flaccid, decreased reflex).

8-14. How can damage to sensory nerve fibers affect reflexes?

Answer 8-14. Damage to sensory nerve fibers may also decrease reflexes by damaging the afferent limb of the reflex arc.

8-15. What is the effect of neuropathy on muscle stretch reflexes?

Answer 8-15. Neuropathy often produces decreased reflexes out of proportion to weakness.

8-16. What are some visceral reflexes that can be tested?

Answer 8-16. Visceral reflexes include: pupillary light reflex, oculocardiac, carotid sinus, bulbocavernosus, rectal (internal sphincter) and orthostatic blood pressure regulation.