228 12 Diseases of the Spinal Roots and Peripheral

a b C5 median n. C6 C7 C8

T1 flexor digitorum superficialis m.

ulnar n.

flexor dig. prof. m.

flexor pollicis longus m. muscular branch anterior antebrachial interosseous n. of ulnar n. to the pronator quadratus m. median n.

supracondylar process of the humerus

pronator quadratus m. pronator palmar branch teres m. tendon of flex. carpi rad. m. palmaris tendon of abductor pollicis brevis m. longus m. palmaris longus m. opponens pollicis m. pronator flexor pollicis brevis m. teres m. (superficial head) flexor carpi radialis m. palmar digital nn. lumbrical mm. I and II

c

Fig. 12.33 Anatomical course and distribution of the median n. a Proximal course. b Course after traversal of the pronator teres m. c Zones of cutaneous innervation in the hand. Syndrome The (CTS) is caused by (me- chanical) compression of the median n. as it passes through the carpal tunnel. It is considerably more com- mon in women than in men and tends to develop around the time of the menopause. It usually affects the dominant hand, but it may affect the nondominant hand, or both. Factors that promote or precipitate the

୵ Fig. 12.34 “Preacher’s hand” due to a proximal left lesion. The hypesthetic area is shaded dark red.

ThiemeARgoOne ThiemeARgoOneBold Peripheral Nerve Lesions 229 development of CTS include hormonal changes (menopause, pregnancy), weight gain, hypothyroidism, diabetes mellitus, and others.

Typical deficits. CTS is characterized by the following manifestations: ¼ in the first stage, which lasts several months or years, the manifestations are subjective: dull pain in the arm at night (brachialgia paresthetica nocturna), ¼ which is felt not merely in the hand, but in the whole up to the shoulder, ¼ wakes the patient from sleep and can be relieved by shaking and massaging the arms, ¼ the fingers are stiff and uncoordinated for a short Fig. 12.35 “Bottle” sign in right median nerve palsy. The thumb time after the patient arises in the morning, cannot be adequately abducted and opposed. ¼ in the more advanced stage, abnormal sensations (paresthesiae) develop and the sense of touch is im- paired, mainly in the thumb and index finger, ¼ careful clinical examination is needed to reveal ob- jectifiable sensory and/or motor deficits.

Examination and diagnostic evaluation. An oc- casional objective finding is point tenderness to pres- sure at the root of the thenar muscles, or a positive Tinel sign (paresthesiae in the radial portion of the palm and the radial fingers induced by a tap on the transverse car- pal ligament). Paresthesiae in the fingers can sometimes be induced by sustained passive hyperflexion or hyper- extension of the wrist (Phalen sign). Only later in the course of CTS can one find a discrete impairment of the Fig. 12.36 Inadequate opposition and pronation of the thumb in sense of touch, particularly in the index finger (e. g., a a patient with a right median nerve lesion. Because the thumb is worsening of two-point discrimination to Œ 5 mm). The insufficiently rotated, the thumbnail is seen tangentially rather than major finding, however, is an inability to abduct the head on. thumb fully, particularly when compared with the nor- mal, opposite side, because of weakness of the abductor Overt CTS is unequivocally demonstrated by a finding of pollicis brevis m. This can be demonstrated by having impaired conduction in the median n. across the carpal the patient grasp a cylindrical object; a “positive bottle tunnel, as revealed by electroneurography (Fig. 12.37). sign” is seen (Fig. 12.35). Impaired opposition of the This study should always be done before any operation thumb is more difficult to observe clinically (Fig. 12.36). is performed. Diminished conduction velocity alone, in

Fig. 12.37 Motor median neuro- graphy in right carpal tunnel syn- drome. The recording is performed 9.2ms over the abductor pollicis m. The 50m/s 55m/s distal motor latency is prolonged (9.2 ms, compared to normal 3.9 ms). The nerve conduction veloci- Diseases of the Spinal Nerve Roots and Peripheral Nerves ties in the arm and forearm are nor- mal. stimulus: wrist 12

2mV 5ms elbow

upper arm

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