Tendon Reflex Amplitude

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Absent with reinforcement

Present but decreased in amplitude and velocity from the normal range and elicited with reinforcement

Normal amplitude and velocity without reinforcement

Increased in amplitude and/or velocity with spread to adjacent site

Increased in amplitude and/or velocity with spread to adjacent site and duplication of the jerk or clonus cutaneous reflexes are noted as present or absent. Tendon reflexes are elicited with a percussion hammer, of which many types are available. The two most commonly used are the hammer developed at the National Hospital for Nervous Diseases at Queen Square in London, and the tomahawk-shaped hammer used most often by American neurologists. The "Queen Square" hammer comes in a variety of sizes. The mallet should have sufficient weight and the handle should be long enough to easily create enough momentum to produce a sharp but nonpainful tap on the desired tendon. The sites at which the tendon reflexes are most commonly tested are listed in Table 15.-4., which notes the myotome level of innervation involved in the reflex arc.

Finger flexor jerks may be obtained in two different ways. The more common method is the one described by Hoffman. The middle finger is held between the second and third fingers of the examiner and the distal phalanx is flicked downward by the examiner's thumb. A positive Hoffman sign is a reflex flexion of the fingers, most easily seen in the thumb. A more reliable way of obtaining this flexion reflex of the fingers was described by Troomner. The examiner lays the fingers of the patient's hand on his own and taps his own fingers. The sudden stretch on all of the patient's fingers elicits a more reliable response, which is a reflex flexion of the fingers that can be felt by the examiner and also observed in the thumb as in the Hoffman's reflex. Like the tendon jerk, the reflex is most apt to be obtained in patients with hyperactive reflexes. However, the reflexes need not be pathologically hyperactive because this reflex can be seen in normal individuals. The reflex has clinical significance when it is asymmetrical and confirms a suspected asymmetry in the tendon jerks. The presence of a Hoffman sign by itself is not necessarily pathological and must be interpreted in the context of other tendon jerks and other signs of an upper motor neuron lesion such as ankle clonus and a Babinski sign.

TABLE 15-4 -- MYOTOMAL INNERVATION OF TENDON REFLEXES

Reflex

Spinal Segment

Peripheral Nerve

Biceps jerk

C5-C6

Musculocutaneous

Brachioradialis

C5-C6

Radial

Triceps jerk

C6-C7

Radial

Flexor finger jerk

C7-C8

Median and ulnar

Knee jerk

L2-L4

Femoral

Ankle jerk

L5,S1-S2

Sciatic

Reflex clonus, the repetitive contraction of a muscle or muscle group, is also obtained by putting a sudden stretch on a muscle. It is most commonly and easily elicited at the ankle. The Achilles tendon is stretched by rapidly dorsiflexing the foot and holding it in the dorsiflexed position. This can be done with the patient in either a sitting or lying position but is generally obtained most reliably in the supine position with the examiner holding the leg flexed at the knee and rapidly dorsiflexing the foot with an upward and outward motion. In the sitting position it may be more readily elicited using a combination of a tap on the tendon with the hammer followed by holding the foot in a dorsiflexed position. In a patient with fully developed ankle clonus, repetitive plantar flexion of the foot can be maintained virtually indefinitely as long as an upward pressure is maintained on the foot. Patellar (quadriceps) clonus can be obtained by producing a quick forcible downward displacement of the patella, which puts a stretch on the patellar or quadriceps tendon. In patients with severe spasticity one may also obtain clonus in the fingers, elicited by the Hoffman or Troomner maneuver, or in the jaw by tapping it with a hammer. Occasionally, one to two beats of clonus can be obtained at the ankle in normal individuals with naturally brisk reflexes. Generally speaking, however, clonus cannot be obtained at any site in the normal individual. The severity of clonus parallels the severity of spasticity and hyperreflexia.

The presence of the flexor reflex in the form of extension or dorsiflexion of the great toe (i.e., the sign described by Babinski) is referred to in many ways. Some report it as the presence or absence of the Babinski sign (see Fig. 15-13 (Figure Not Available) ). To avoid confusion, some prefer to describe the response of the great toe to stimulation of the plantar surface of the outer sole. Thus, the plantar (or toe) response is described as flexor or extensor. Another colloquial way to refer to the presence of a Babinski sign is to describe it as an "up going toe." The preference of the author is to refer to it as a flexor or extensor plantar response.

The extensor plantar response is most reliably obtained with the method of stimulation described by Babinski. Others have described additional methods of stimulation that also produce the extensor toe response. [31] This reflects an expansion of the reflexogenous zone or receptive field when the upper motor neuron lesion is more complete and/or mature, especially in patients with spinal cord lesions. The most commonly used alternative to the Babinski method is the Chaddock maneuver, which consists of rubbing the lateral surface of the foot with the edge of a tongue blade or key from the heel to the little toe. The Oppenheim maneuver involves applying heavy pressure with the thumb and forefinger to the anterior surface of the tibia and stroking downward from the infrapatellar region toward the ankle. Bing obtained the extensor toe response by pricking the dorsum of the foot or great toe with a pin, and Gordon obtained it by squeezing the calf muscles. These other maneuvers are mainly useful in the patient who is very ticklish in whom it is difficult to differentiate spontaneous withdrawal from reflex responses. Another sign of upper motor neuron disease is the crossed adductor reflex.

Diffuse cerebral disease can unmask reflexes normally present only in the infant. These are generally referred to as primitive reflexes. They are sometimes referred to as frontal release signs because they are most commonly seen in demented individuals with frontal lobe disease. The snout reflex is a component of the suck reflex in which there is a puckering movement of the lips in response to pressure or light tapping on the lips. The facial jerks are usually increased in this situation, and it may not be possible to differentiate between the two. The most convincing demonstration that this is a primitive reflex occurs when stroking the cheek elicits the same response it would in an infant or if visual presentation of an object moving toward the mouth produces the response ("visual suck"). The grasp reflex may also be unilateral or asymmetrical and reflects unilateral or asymmetrical frontal lobe disease. It is elicited by diverting the patient's attention and casually stroking the palm of the hand with two or three fingers. If the reflex is present, the examiner's fingers will be grasped with increasing force; the harder the examiner tries to extricate his fingers, the harder the patient grips. Patients may literally be lifted off the bed and the fingers pried open only with great difficulty after the examiner has put the arm back in a resting position. The palmomental reflex is obtained by scratching the palm of the hand and observing the reflex contraction of the mentalis muscle of the chin. This reflex is seen more often in demented individuals but may also be seen in normals and is too unreliable to be used as a diagnostic sign of dementia.

Stretch reflexes can also be obtained by putting a sudden stretch on muscles that lack a tendon. This is done by directly tapping the muscle with the aid of the examiner's fingers and the reflex hammer. The two best examples are the facial jerk and the jaw jerk. To obtain the facial jerk, the examiner first stretches the skin of the patient's nasolabial fold with the index and middle finger of one hand and then taps these fingers with the reflex hammer, producing a reflex contraction in the underlying facial muscles. A reflex contraction in the muscles of mastication, the jaw jerk, is more easily obtained by simply tapping the point of the chin with the reflex hammer. Usually the examiner's fingers are put on the point of the chin and interposed between the blow of the hammer and the patient's chin.

As in the detection of weakness, it is the pattern of changes in the reflexes that is sought as an aid in localization. For upper motor neuron lesions, the distribution of hyperreflexia is the most valuable aid. The most common pattern is one of asymmetry between the sides because of a lesion in one cerebral hemisphere. The presence of symmetrical hyperreflexia, spasticity, clonus, and Babinski signs indicates an interruption of the corticospinal tracts bilaterally, which could be a result of bilateral hemispheral disease or a brain stem or spinal cord lesion. The differentiation between these possible sites can usually be determined by associated signs ( . TableJ 5-5 ). If the disease is hemispheral, the corticobulbar tracts are also interrupted, producing a pseudobulbar palsy with spastic dysarthria, dysphagia, and increased facial and jaw jerks. Other signs of diffuse cerebral dysfunction may also be present such as dementia. If the lesion is in the brain stem, bilateral corticospinal dysfunction is often associated with disturbances of consciousness or cranial nerve dysfunction. A cervical cord lesion produces hyperreflexia and spasticity

248

TABLE 15-5 -- CLINICO-ANATO

MICAL CORRELATIONS FOR DISORDERS AFFECTING STRENGTH AND REFLEXES

Anatomic Site of Damage

Strength and Reflex Findings

Other Neurological and Medical Findings

Common Etiologies

Comments

UPPER MOTOR NEURON SYNDROMES

Pyramidal lesions

Cortex and subcortex

Brain stem

Spinal cord

Diffuse excitation of internuncial pool

Progressive spinal atrophy syndrome

Radiculopathy

Plexopathy

Peripheral neuropathy, mononeuropathy

Contralateral hemiparesis, hyperreflexia, spasticity, Babinski's sign

Large bilateral lesion: tetraparesis, bilateral hyperreflexia, Babinski's sign

Small lesions: contralateral hemiparesis, hyperreflexia, Babinski's sign

Tetraparesis or paraparesis, bilateral hyperreflexia, Babinski's sign, normal jaw jerk

Weakness of ocular, facial, or bulbar muscles (cephalic tetanus), diffuse hyperreflexia

Progressive weakness, muscular atrophy, loss of tendon reflexes

Weakness of individual or combinations of muscles in one limb, reduction or loss of reflexes in myotomal pattern

Weakness and loss of tendon reflexes of muscles supplied by more than one spinal or peripheral nerve

Weakness of muscles supplied by single peripheral nerve

UPPER MOTOR NEURON SYNDROMES

Cortex:

Left: aphasia, apraxia

Right: constructional apraxia

Homonymous hemianopia on paretic side

Subcortex:

No aphasia or sensory loss

Coma, decerebrate posturing

Ipsilateral cranial nerve palsy

Sensory level, no cranial nerve signs

Rigidity, tetanic seizures

Stroke, neoplasm

Stroke, trauma

Trauma, multiple sclerosis

Tetanus, stiff-person syndrome

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