spinal nerves and roots

clinical localization lectures

1. 4. Spinal Nerve and Root By Dr.Rzgar hamed

2. Anatomy of the Spinal Nerves and Roots The sensory fibers from the peripheral nervous system enter the spinal cord in the dorsal roots and have their perikarya in the dorsal spinal root ganglia . The dorsal roots enter the cord in the dorsolateral sulcus. The Motor fibers arise from the motor neurons located in the ventral horns of the spinal cord and exit the cord as the ventral roots . The ventral and dorsal roots unite and combine with autonomic fibers to form the mixed spinal nerve , which then travels through the intervertebral foramen. After emerging from the foramen, the spinal nerve divides into anterior and posterior primary rami. The smaller posterior primary rami supply the skin on the dorsal aspect of the trunk with sensory fibers and also send motor fibers to the longitudinal muscles of the axial skeleton. The anterior primary rami supply the limbs , nonaxial skeletal muscles, and skin of the lateral and anterior trunk and neck (by way of the lateral cutaneous and anterior cutaneous branches , respectively). The anterior primary rami also communicate with the sympathetic ganglia through white and gray rami communicantes . There are 31 pairs of spinal nerves—8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal.

3. Principles of Spinal Nerve and Root Localization Sensory Symptoms Irritative lesions of a dorsal root result in radicular pain or root pain , precipitated by maneuvers that cause increased intraspinal pressure or stretching of the dorsal nerve root (e.g., coughing, straining, sneezing, Valsalva maneuver, or spine movements). may be associated with paresthesias or dysesthesias in the area involved. Destructive dorsal root lesions result in hypesthesia or anesthesia Motor Signs Ventral root lesions result in weakness and atrophy in the myotomal distribution of the affected root. Fasciculations may be evident in the affected muscle. Reflex Signs with ventral or dorsal lesions, hypo- or areflexia occurs in the muscle subserved by the affected spinal root.

4. Etiology : The most common disc prolapse in the cervical region is at the C6–C7 interspace, In the lumbar region, the most common disc prolapse is at the L4–L5 or L5–S1 Certain generalized peripheral nervous system diseases have a predilection for the spinal roots (e.g., Guillain – Barré syndrome). Herpes zoster in the sensory dermatomes (thoracic level) Lyme disease, especially affecting the fifth cervical dermatome or lower thoracic levels Diabetes mellitus may cause thoracic root pain or thoracoabdominal neuropathy , presenting with severe abdominal or chest pain, often not radicular in character. >> The presence of dysesthesias and abnormal findings on sensory examination of the trunk aid in the diagnosis of these diabetic neuropathies. >> may rarely present with focal, unilateral protrusion of the abdominal wall ( pseudohernia ), which may be associated with spontaneous, burning abdominal pain and hyperpathia or which may be painless . HIV cytomegalovirus infection, metastasis from systemic lymphoma

5. The Localization of Nerve Root Syndromes C1 lesion : P urely motor symptoms (has no dorsal root ): muscles that support the head, fix the neck, assist in neck flexion and extension, and tilt the head to one side. C2 lesion : Sensory symptoms : shown The motor supply : same as C1 plus helps the sternocleidomastoid muscle (head rotation and flexion), which is predominantly innervated by XI.

6. C3 lesions: Sensory : the lower occiput, the angle of the jaw, and the upper neck Motor : >> the scalene and levator scapulae muscles of the neck ,in the trapezius (shoulder elevation), this last muscle being predominantly innervated by the spinal accessory nerve (cranial nerve XI). >> Diaphragmatic paresis (phrenic nerve receives some of its fibers from the C3 segment) Irritation of the C3 nerve root may cause a painful, burning, red ear ( red ear syndrome ) that may also occur with temporomandibular joint dysfunction and with thalamic lesions . C4 lesion: Sensory : the lower neck. Motor : the scalene and levator scapulae muscles (lateral neck flexion and scapular rotation, respectively), rhomboid muscles (scapular elevation and adduction), trapezius muscle (shoulder elevation), and some muscles of the neck. Diaphragmatic paresis may also occur because some fibers reach the phrenic nerve. There is no reflex impairment.

7. C5 lesion: Sensory: neck , shoulder, and upper anterior arm pain, the lateral arm Motor : >> the deltoid (pure C5 , axillary nerve) and biceps (both C5 and C6, musculocutaneous nerve) >> examine shoulder abduction and elbow flexion. Diaphragmatic paresis may rarely occur owing to C5 fibers reaching the phrenic nerve. Reflex : The biceps reflex ( subserved by segments C5–C6) and the brachioradialis reflex (C5–C6) may be depressed.

8. C6 lesion : Commonly with disc herniation at the C5–C6 vertebral level. A monoradiculopathy affecting the C6 nerve root is the second most common level of cervical radiculopathy after lesions of the C7 level Sensory: >>pain in the lateral arm and dorsal forearm. >> the lateral forearm, lateral hand, and the first and second digits. Motor : >> The wrist extensor (radial nerve) and the biceps (musculocutaneous nerve) >> However , the wrist extensor group is also partly innervated by the C7 root (ulnar nerve), and the biceps muscle is also partly innervated by the C5 root (musculocutaneous nerve). >> ulnar deviation during wrist extension. Reflex: The biceps reflex and the brachioradialis reflex may be depressed. An “inverted radial reflex: tapping the tendon of the brachioradialis muscle elicits no response by the brachioradialis but a brisk contraction of the finger flexors innervated by the C8–T1 segments.

9. C7 lesion: C6–C7 disc herniation Sensory : >> pain in the dorsal forearm, subscapular >> sensory disturbance in the third and fourth digits. Motor : >> The triceps muscle (radial nerve), wrist flexors (median and ulnar nerves), and finger extensors (radial nerve) >> With C7 lesions, wrist flexion results in an ulnarward deviation . Reflex: The triceps reflex (C7–C8) may be depressed. >> Pseudomyotonia : Muscle relaxation is normal but attempts to extend the fingers produce paradoxical flexion of the fingers, probably as a result of misdirected regeneration of C7 nerve root fibers

10. C8 lesion : C7–T1 herniation. Sensory: >> pain and sensory change in the medial arm and forearm, hand and on the fifth digit. Motor : The muscles of finger flexion (median and ulnar nerves) Reflex: The finger flexor reflex (C8–T1) may be depressed. ipsilateral Horner syndrome : due to sympathetic interruption.

11. T1 lesion: Motor : >> finger abduction(T1; ulnar nerve) and finger adduction (C8 , T1; ulnar nerve) To test finger adduction, place a piece of paper between two of the patient’s extended fingers and attempt to pull the paper away. Sensory : the upper half of the medial forearm and the medial portion of the arm. Reflex: The finger flexor reflex (C8–T1) may be depressed. ipsilateral Horner syndrome .

12. T2–T12 lesions: Motor >> intercostals and the rectus abdominal muscles (difficult to examine individually) >> Beevor’s sign is present when the umbilicus of the patient is drawn up or down, or to one side or the other, when the patient is a quarter way through a sit-up . Sensory the nipples ( T4) the xyphoid process ( T6) the umbilicus ( T10 ) the inguinal ligament (T12 ).

13. L1 lesion: Sensory : the inguinal region. Motor: Lower abdominal paresis L2 lesion : Sensory : the anterior thigh. Motor : Paresis may be present in the pectineus (thigh adduction, flexion, and eversion), iliopsoas (thigh flexion), sartorius (thigh flexion and eversion), quadriceps (leg extension), and thigh adductors. Reflex: The cremasteric reflex (L2) may be depressed . >> With upper lumbar root lesions (L2–L4), the result of bent-knee pulling test is often positive . The examiner pulls the half-prone patient’s knee backward while putting forward pressure on the buttock; the test result is positive when lumbar radicular pain is elicited.

14. >> Drooping of the testicle (“testicular ptosis”) with L2 nerve root lesions, (normally left testicle commonly hangs lower than the right by 1 cm) L3 lesion Sensory : the lower anterior thigh and medial aspect of the knee. Motor : as L2 Reflex : The patellar reflex (L2–L4) may be depressed.

15. L4 lesion: Sensory: >> lower back, buttock, anterolateral thigh, and anterior leg pain . >> Sensory disturbances : on the knee and the medial leg. Motor: Paresis occurs variably in the quadriceps (leg extension), sartorius (thigh flexion and eversion), and tibialis anterior (foot dorsiflexion and inversion). Reflex: The patellar reflex (L2–L4) may be depressed. >> Rarely , neurogenic hypertrophy of the tibialis anterior muscle may occur with a chronic L4 lesion The four tests of quadriceps strength included: single leg sit-to-stand test: weakness was detected in 61 % of cases step-up test : 42%, knee-flexed manual muscle testing : 27% knee-extended manual muscle testing: 9%

16. L5 lesion: Sensory: >> lower back, buttock, lateral thigh, and anterolateral calf pain. >> on the lateral leg, the dorsomedial foot, and the large toe. Motor: weakness in >> the extensor hallucis longus(L5; deep peroneal nerve ): dorsiflexion of the big toe >> the extensor digitorum (L5 ; deep peroneal nerve) : dorsoflexion of the lateral four toes >> the gluteus medius (L5; superior gluteal nerve ): abduction of the hip, it is important in the differentiation of a peroneal nerve palsy from an L5 nerve root injury Reflex: >> There is no deep tendon reflex to test the integrity of the L5 nerve root >> both the patellar (L2–L4) and Achilles (S1–S2) reflexes are spared. The straight leg raise : the accuracy of the straight leg test as 91% sensitive and 26% specific in L5 root lesion. If raising the opposite leg causes pain (cross or contralateral straight leg raising), the sensitivity is 29% and the specificity is 88%

17. S1 root lesion Sensory: >> lower back, buttock, lateral thigh, and calf pain >> Sensory disturbances occur on the little toe, lateral foot, and most of the sole of the foot. Motor : paresis in >> the peroneus longus and brevis(S1 ; superficial peroneal nerve) : evertors of the ankle and foot >> the gastrocnemius–soleus muscles (S1, S2; tibial nerve ) :extensors of the foot >> the gluteus maximus (S1 ; inferior gluteal nerve): extensor of the hip . Rarely , an S1 radiculopathy may result in unilateral calf enlargement Reflex >> The Achilles reflex is innervated by S1 depressed

18. S2–S5 lesion: Sensory concentric rings around the anus. Motor the intrinsic muscles of the foot. Reflex >> The anal wink reflex is supplied by the S2–S4 nerve roots will be absent. Anal Sphincter and bladder sphincter are impaired

19. Nerve Root Syndromes