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.

4. 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.

5. 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

8. The Localization of Nerve Root
Syndromes
C1 lesion :
• Purely 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.

9. 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.

10. 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.

11. 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.

13. 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

14. 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.

15. 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.

16. 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).

17. 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.

18. >> 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.

19. 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:
(a) single leg sit-to-stand test: weakness was detected in 61% of cases
(b) step-up test : 42%,
(c) knee-flexed manual muscle testing : 27%
(d) knee-extended manual muscle testing: 9%

21. 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%

23. 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

25. 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

28. Nerve Root Syndromes