REIDER PART 264

324_Chapter 8_Cervical and Thoracic Spine

hyperreactive. The examiner must make this subjective assessment through comparison with patients examincd in the past. A normal rcflcx typically produces a palpabie contraction, often associated with a slight movement of the limb. Strong or violent responses to reflex testing are suspicious for hyperreactivity. Hyporeactive reflexes are very difficult to elicit or are completely absent. Generalized areflexia may be present in metabolic States such as hypercalcemia. A lower motor neuron lesion is characterized by weakness and hyporeflexia, whereas an upper motor neuron lesion is typified by hyperreflexia and the presence of pathologic reflexes such as the Babiński reflex. A unilaterally diminished or absent reflex is the most common abnormal finding and suggests nerve injury at the root level or distal to it.

Plantar Reflex. The Babiński sign is a pathologic reflex that indicates upper motor neuron involvement. To test the plantar reflex, the examiner asks the patient to sit comfortably with the fcct dangling from the examination table. The examiner grasps the patients foot with one hand, then gently strokes the lateral border of the sole of the foot beginning about the level of the heel and moving distally (Fig. 8-40A). In a normal patient, the initial response is a downward reflection of the great toe (Fig. 8-40B), although the toes may subsequently dorsiflex. When the Babiński sign is present, the toes immediately dorsiflcx when the plantar surface of the foot is stroked (Fig. 8-40C).

Clonus. Clonus is another sign of hyperreflexia that suggests an upper motor neuron lesion. It is usually asscsscd