REIDER PART 265

Chaptfr 8_Cervical and Thoracic Spine 325

Figurę 8-41. Eliciting anklc clonus.

with thc paticnt sitting on the examination table. While stabilizing the patients leg with one hand, the examiner grasps the patients forefoot with the other hand and ąuickly and forcefully pushes it into dorsiflexion (Fig. 8-41). When clonus is present, such a sudden dorsiflexion produces a rhythmic involuntary motion that alternates between plantar flexion and dorsiflexion. Each cycle of motion is called a beat of clonus. One or two beats of clonus may be present in otherwise normal individuals. When clonus is sustained beyond two beats, an upper motor neuron lesion, such as proximal spinał cord com-pression, should be suspccted.

Cervical Spinał Stenosis. Cervical spinał stenosis typi-cally produces lower motor neuron findings at the level of the lesion and upper motor neuron deficits distal to the level of the lesion. For example, in the case of cervical stenosis at the C5-C6 level, one would normally flnd lower motor neuron signs of the C6 nerve root and upper motor neuron signs distal to that. Thus, in this particular example, the lower motor neuron deficit would be mani-fested by weakness in the biceps and the wrist extensors with diminution of the biceps and the brachioradialis reflexes. Upper motor neuron involvement distal to the level of the lesion would be reflected in hyperreflexia of the triceps, the quadriceps, and the gastrocnemius reflexes. Other upper motor neuron signs such as clonus and the Babiński reflexes might or might not be present. Abdominal Muscle Ref!exes. Abdominal muscle reflexes may be testcd as a method of screening for thoracic spinał cord compression. To assess abdominal reflexes, the patient is positioned comfortably in a supine position with the abdomen cxposed. The handle of the reflex hammer is then gently strokcd across the abdomen in a radial manner beginning at the umbilicus and proceeding toward the 2-o’clock, thc 4-o’clock, the 8-o’clock, and the 10-o’clock positions, in succession (Fig. 8-42). Normally, such stimulation should cause the abdominal musculaturc to iiwoluntarily contract, result-ing in movement of the umbilicus in the direction of the ąuadrant being stimulated. Absence of the normal response indicates thoracic spinał cord compression on the side of the diminished reflex. Remembering that the upper abdominal musculature is innervated by the T7 through T10 nerve roots and the lower abdominal musculature is innervated by the T10 through LI nerve roots

Figurę 8-42. A and B, Eliciting abdominal reflexes. (Arrows in B indicate the direction of stroking.)