Intercostals: The intercostal muscles are segmentally innervated and are difficult to evaluate individually.

Rectus Abdominis: The rectus abdominis muscles are segmentally innervated by the primary anterior divisions of T5-T12 (L1), with the umbilicus the dividing point between T10 and T11.

Beevor’s sign (Fig. 2-1) tests the integrity of the segmental innervation of the rectus abdominis muscles. Ask the patient to do a quarter sit-up. While the patient is doing this, observe the umbilicus. Normally, it should not move at all when the maneuver is performed. If, however, the umbilicus is drawn up or down or to one side or the other, be alerted to possible asymmetrical involvement of the anterior abdominal muscles. Lesions of the spinal cord or roots between T10 and T12 will cause weakness of the lower part of the muscle, and thus a positive Beevor’s side with the umbilicus moving upward during the quarter sit-up.

Sensory areas for each nerve root are shown in Figure 4-1. The sensory area for T4 crosses the nipple line, T7 the xiphoid process, T10 the umbilicus, and T12 the groin. There is sufficient overlap of these areas for no anesthesia to exist if only one nerve root is involved. However, hypoesthesia is probably present.

There is no specific muscle test for each root. The muscles that are usually tested are the iliopsoas (T12-L3), the quadriceps (L2-L4), and the adductor group (L2-L4).

Iliopsoas: (Branches from [T12], L1-L3): The iliopsoas muscle is the main flexor of the hip (Fig. 2-2). To test it, instruct the patient to sit on the edge of the examining table with the legs dangling. Stabilize the pelvis by placing your hand over the patient’s iliac crest and have the patient actively raise their thigh off the table. Now place your other hand over the distal femoral portion of the knee and ask the patient to raise the thigh further as you resist (Fig. 2-3). Determine the maximum resistance
the patient can overcome. Then repeat the test for the opposite iliopsoas muscle and compare muscle strengths. Because the iliopsoas receives innervation from several levels, a muscle that is only slightly weaker than its counterpart may indicate neurologic problems.

In addition to possible neurologic pathology, the iliopsoas may become weak as a result of an abscess within its substance; the patient may then complain of pain during muscle testing. The muscle may also become weak as a result of knee or hip surgery.

Quadriceps: L2- L4 (Femoral Nerve): To test the quadriceps functionally, instruct the patient to stand from a squatting position (Fig. 2-4). Note carefully whether the patient stands straight, with the knees in full extension, or whether one leg is used more than the other. The arc of motion from flexion to extension should be smooth. Occasionally, the patient may be able to extend the knee smoothly only until the last 10°, finishing the motion haltingly and with great effort. This faltering in the last 10° of extension is called extension lag; it occurs because the last 10° to 15° of knee extension requires at least 50 percent more muscle power than the rest (according to Jacqueline Perry). Extension lag is frequently seen in association
with quadriceps weakness. Sometimes, the patient may be unable to extend his knee through the last 10° with even the greatest effort (Fig. 2-5).

To test the quadriceps manually, stabilize the thigh by placing one hand just above the knee. Instruct the patient to extend his knee as you offer resistance just above the ankle joint. Palpate the quadriceps during the test with your stabilizing hand (Fig. 2-6). Note that the quadriceps weakness can also be due to a reflex decrease in muscle strength following knee surgery or to tears within the substance of the muscle itself.

Hip Adductor Group: L2-L4 (Obturator Nerve): Like the quadriceps, the hip adductors can be tested as a massive grouping (Fig. 2-7). Have the patient lie supine or on their side and instruct the patient to abduct the legs. Place your hand on the medial sides of both knees and have the patient adduct their legs against your resistance (Fig. 2-8). Determine the maximum resistance they can overcome.

Although the patellar tendon reflex is supplied by L2-L4, it is predominantly L4 and will be tested as such.

Nerves from L1 to L3 provide sensation over the general area of the anterior thigh between the inguinal ligament and the knee. The L1
dermatome is an oblique band on the upper anterior portion of the thigh, immediately below the inguinal ligament. The L3 dermatome is an oblique band on the anterior thigh, immediately above the kneecap. Between these two bands, on the anterior aspect of the mid thigh, lies the L2 dermatome (Fig. 2-9).

Sensory testing, with its bands of individual dermatomes, is a more accurate way of evaluating neurologic levels T12-L3 than motor testing, which lacks individual representative muscles. There are also no representative reflexes for these levels, making it even more difficult to diagnose an exact neurologic level. Neurologic levels L4, L5, and S1 are represented by individual muscles, dermatomes, and reflexes, and are easier to diagnose.

Tibialis Anterior: L4 (Deep Peroneal Nerve): The tibialis anterior muscle is predominantly innervated by the L4 segmental level; it also receives L5 innervation (Figs. 2-10 and 2-11). To test the muscle in function, ask the patient to walk on his heels with his feet inverted. The tendon of the tibialis anterior muscle becomes visible as it crosses the anteromedial portion of the ankle joint and is quite prominent as it proceeds distally toward its insertion. Patients with weak tibialis anterior muscles are unable to perform this functional dorsiflexion-inversion test; they may also exhibit “drop foot,” or steppage gait.

To test the tibialis anterior manually, instruct the patient to sit on the edge of the examining table. Support his lower leg, and place your thumb in a position that makes him dorsiflex and invert his foot to reach it. Try to force the foot into plantar flexion and eversion by pushing against the head and shaft of the first metatarsal; palpate the tibialis anterior muscle as you test it (Fig. 2-12).

Patellar Tendon Reflex: The patellar tendon reflex is a deep tendon reflex, mediated through nerves emanating from the L2-L4 nerve roots (predominantly from L4). For clinical application, the patellar tendon reflex should be considered an L4 reflex; however, because it receives innervation from L2 and L3 as well as from L4, the reflex will still be present, although significantly weakened, even if the L4 nerve root is completely severed. The reflex is almost never totally absent. However, in primary muscle, nerve root, or anterior horn cell disease, the reflex can be totally absent.

To test the patellar tendon reflex, ask the patient to sit on the edge of the examining table with the legs dangling. (The patient may also sit on a chair with one leg crossed over his knee or, if the patient is in bed, with the knee supported in a few degrees of flexion) (Fig. 2-13). In these positions, the infrapatellar tendon is stretched and primed. Palpate the soft tissue depression on either side of the tendon to locate it accurately, and attempt to elicit the reflex by tapping the tendon at the level of the knee joint with a short, smart wrist action. If the reflex is difficult to obtain, reinforce it by having the patient clasp his hands and attempt to pull them apart as you tap the tendon. This is known as the Jendrassik maneuver. It prevents the patient from consciously inhibiting or influencing his or her response to reflex testing. Repeat the procedure on the opposite leg, and grade the reflex as normal, increased, decreased, or absent. To remember the neurologic level of the reflex, associate the fact that four muscles constitute the quadriceps muscle with the L4 of the patellar tendon reflex (Fig. 2-14).

The reflex may be affected by problems other than neurologic pathology. For example, if the quadriceps has been traumatized, if the patient has undergone recent surgery to the knee, or if there is knee joint effusion, the reflex may be absent or diminished.

The L4 dermatome covers the medial side of the leg and extends to the medial side of the foot. The knee joint is the dividing line between the L3 dermatome above and the L4 dermatome below. On the leg, the sharp crest of the tibia is the dividing line between the L4 dermatome on the medial side and the L5 dermatome on the lateral side (Fig. 2-15).

Extensor Hallucis Longus: L5 (Deep Branch of the Peroneal Nerve): The tendon of the extensor hallucis longus passes in front of the ankle joint lateral to the tibialis anterior, which is predominately innervated by L4. Test it functionally by having the patient walk on his heels, with his feet neither inverted nor everted. The tendon should stand out clearly on the way to its insertion at the proximal end of the distal phalanx of the great toe. To test the extensor hallucis longus manually, have the patient sit on the edge of the table. Support the foot with one hand around the calcaneus and place your thumb in such a position that the patient must dorsiflex his great toe to reach it. Oppose this dorsiflexion by placing your thumb on the nail bed of the great toe and your fingers on the ball of the foot; then pull down on the toe (Fig. 2-19A). If your thumb crosses the interphalangeal joint, you will be testing the extensor hallucis brevis as well as the longus; make certain that you apply resistance distal to the interphalangeal joint so that you are testing only the extensor hallucis longus. Note that a fracture of the great toe or other recent trauma will produce apparent muscle weakness in the extensor hallucis longus.

Extensor Digitorum Longus and Brevis: L5 (Deep Peroneal Nerve): Test the extensor digitorum longus in function by instructing the patient to walk on his heels, as he did for the extensor hallucis longus. The tendon of the extensor digitorum longus should stand out on the dorsum of the foot, crossing in front of the ankle mortise and fanning out to insert by slips into the dorsal surfaces of the middle and distal phalanges of the lateral four toes.