Clinical Geriatrics

When examining the musculoskeletal system, neurological aspects must be considered. Strength testing, as discussed in Part I of this article (Clinical Geriatrics 2005;13[11]: 16-24), helps to assess whether a pattern of muscular weakness is due to a spinal nerve problem, or other musculoskeletal diseases. Examining the reflexes and the sensory system helps to differentiate neuronal damage from musculoskeletal pathology. Weakness associated with reflexive changes and discrepancies within the sensory system may indicate the nervous system as the culprit that is causing disease. Furthermore, evidence gathered from the neurological exam can determine if a lesion originates in the central nervous system versus the peripheral nervous system.

REFLEXES
Reflexes are involuntary contractions of a muscle brought out by the activation of muscle spindles. They are elicited by a sudden stretch of the muscle induced by a brisk hammer strike on the muscle tendon or the muscle itself. The hammer should strike with a quick, smooth, and direct motion. Note the speed, force, and amplitude of the reflex response, and compare the right and left sides. Decreased reflexes are a sign of spinal nerve and peripheral nerve damage. Entrapment neuropathies, such as that occurring in radial palsies or polyneuropathies in HIV and Guillain-Barré syndrome, present with diminished reflexes. On the contrary, patients presenting with hyperreflexia, clonus, or a Babinski sign may have an upper motor neuron lesion of the central nervous system. This is seen in patients with brain tumors, strokes, and multiple sclerosis.

Fasciculations, or muscle twitches that are too weak to move limbs but are easily seen and felt by patients, should not be confused with a muscle reflex. These tiny contractions of individual muscle fibers are usually benign and can also be present in patients with mineral deficiencies. When accompanied by muscle weakness, fasciculations are a sign of lower motor neuron disease and are characteristic in patients with neurological diseases, such as amyotrophic lateral sclerosis (ALS). They tend to appear in the proximal muscles early on in the disease, and then more distally as ALS progresses.1

Methods of reflex testing of major muscles and their associated spinal nerves are shown in Tables I and II. It is important to note that there are different ways of testing reflexes, as in the ankle reflex. The sensitivity and reproducibility of reflex testing using the different techniques are poor.2 Therefore, interpretations of the reflexes made in light of other physical signs, such as muscle strength or sensory loss, can provide a clearer picture of whether deficits are real.

If patients are having difficulty relaxing for the examiner to check the reflexes, a distracting method, called reinforcement, is used to bring out the reflex. For instance, when checking the patellar reflex patients are asked to hold their hands together with the tips of their fingers and pull outward. This is called the Jendrassik’s maneuver, which isometrically activates the muscles in the upper extremities, causing the patellar reflex to be brought out. The mechanism of potentiation of the reflex remains uncertain.3

GRADING OF MUSCLE REFLEXES
In addition to comparing reflex responses on the right and left side of a patient’s extremities, it is important to observe the amplitude and velocity of the response. The National Institute of Neurological Disorders and Stroke (NINDS) created a scale to describe the myotatic reflex (Table III).4 Its reliability and reproducibility has been studied and accepted internationally. Four neurologists, who received training from different countries, randomly and blindly evaluated the deep tendon reflexes of 80 subjects.5 They were trained with the same type of reflex hammer and employed the same techniques.