Myeloradiculopathy is the clinical presentation of both upper motor neuron signs and symptoms along with lower motor neuron symptoms as discussed earlier. The result is a very confusing picture of weakness, pain, and spasticity. The lower motor neuron symptoms, like weakness, are seen more commonly in the upper extremities and are caused by stenosis in the upper cervical levels. Upper motor neuron symptoms such as spasticity and incoordination are more prevalent in the lower cervical levels below the lesion and the lower extremities. This syndrome is seen most often in patients with cervical spinal canal stenosis in which there is compression of both the cord and the nerve roots (26). The combination of central canal and foraminal narrowing results in deformity of the cord and individual nerve roots. It is not unusual for these patients to have had at least a workup, if not surgery, for peripheral neuropathy or entrapment before seeing a spine surgeon.

The spine has two essential tasks: to maintain posture and to protect the neurologic elements. Many different disease processes can lead to instability of the cervical spine. When the spine is unable to fulfill its normal function, the mechanical stimulation can result in myelopathic symptoms. As the cervical spine subluxes out of normal
alignment, the cord and nerve roots may be compressed or irritated (6).

The third cervical nerve root is rarely involved in degenerative disease of the cervical spine, owing to the normally limited amount of motion at the C2-C3 disk. The dermatomal pattern of this root radiates over the dorsal upper neck onto the occiput and the ear. There is no distinct motor function for this root, and numbness is unusual. Headache pain may be confused with a C3 radiculopathy (7, 8 and 9).

The C3-C4 disk has more motion than C2-C3 and is therefore more commonly involved in radicular pain. The pattern of C4 root pain is at the base of the neck, out over the medial shoulder, and inferior to the level of the scapula. The fourth root lacks a definitive motor function, but pain may be provoked by neck extension. Although the fourth root controls diaphragm function and is of concern in a patient with a spinal cord injury, radicular problems of the fourth root rarely affect diaphragmatic function (7, 8 and 9).

Herniation of the C4-C5 disk is less common than at the levels below. The sensory distribution of C5 is from the base of the neck to the top of the shoulder and down onto the lateral upper arm. This may be difficult to differentiate from shoulder pathology. A thorough evaluation of shoulder motion is necessary along with the neurologic examination to differentiate cervical disease from shoulder pathology. Most importantly, internal and external rotation of the shoulder, along with strength testing of the rotator cuff muscles, must be documented. Some patients with fifth root pathology may develop a frozen shoulder as a consequence of their radicular pain. Motor involvement results in weakness of shoulder abduction (deltoid) and elbow flexion (biceps). This may appear similar to an acute rotator cuff tear, but without tenderness over the shoulder. Complete paralysis of the deltoid may be quite disabling because the patient has difficulty using the affected arm for daily activities, especially those that require overhead motion. Careful examination may demonstrate weakness of external shoulder rotation (supraspinatus and infraspinatus). There may also be an element of biceps weakness with C5 root lesions and possible suppression of the biceps reflex (7, 8 and 9).

The C5-C6 disk is most commonly affected by degenerative disk disease and, along with the C6-C7 disk, represents one of the two most common levels for disk herniation. The pain of a sixth root lesion radiates from the base of the neck, along the biceps muscle and lateral forearm, and onto the dorsum of the hand and fingers on the radial side, involving the tips of the first two digits. Patients may note tenderness of the biceps muscle during examination. Biceps weakness is often subtle and unnoticed by the patient until demonstrated by examination and may be accompanied by weakness of wrist extension. More subtle muscular changes involve the infraspinatus, serratus anterior, supinator, and extensor pollicis. The clinical picture often includes pain in the proximal arm, with numbness into the hand (7, 8 and 9).

C7 radiculopathy is a common occurrence because of the frequency of both disk herniations and degenerative changes at the C6-C7 level. Patients trace the pain distribution across the dorsal shoulder, along the triceps and dorsolateral forearm, to the middle digit. Loss of the triceps reflex is a reliable indicator of seventh root dysfunction, often with triceps weakness that may not be noticed by the patient. An athletic patient whose sport involves forceful elbow extension or a manual laborer who performs overhead activities may notice triceps weakness. The examiner must take care to avoid confusing a patient who tries to substitute internal rotation of the humerus to compensate for triceps weakness. The C7 root also provides some motor function to the pectoralis major muscle that may be evaluated by testing humeral adduction. Additional muscles included in the C7 neurologic level are the pronator, extensor digitorum, and latissimus dorsi, along with wrist flexion, primarily from the flexor carpi radialis (7, 8 and 9).

Herniation of the disk at the C7-T1 level is unusual. The C8 nerve root provides sensation to the ulnar side of the hand, primarily the fourth and fifth digits, and to the ulnar side of the forearm. Pain and numbness are distributed the same as with an ulnar nerve lesion at the elbow. Strength testing of the C8 root involves primarily the small muscles of the hand. Finger flexion, as powered by the flexor digitorum profundus and superficialis muscles, is under control of the eighth root. In addition, the intrinsic muscles, especially the interossei, which control finger abduction, are innervated by C8 and T1. Loss of motor function can be very disabling, with weakness of the power grip, normally from the ulnar side of the hand. There may also be difficulties with turning keys or holding small objects owing to weakness, especially of the first dorsal interosseous muscles (7, 8, 9 and 10).

Clinical presentations of cervical disk herniation are quite variable, depending on the level involved. Generally, patients note the onset of neck pain followed by radiation of the pain into the characteristic dermatomal pattern of the nerve root involved. Weakness is often not noted immediately because pain inhibition markedly limits activities. Just as in individuals with shoulder pain, these patients are more comfortable sleeping in a reclining chair than in a bed. Some present with a torticollis rotating away
from the painful side in an unconscious effort to open the neuroforamen and lessen the arm pain. Extension of the cervical spine exacerbates pain. Patients with acute disk herniation may present in a very characteristic posture with the shoulder abducted and the forearm resting on top of the head. This promotes lateral flexion toward the opposite side to open the affected neuroforamen, and the abduction relieves tension on the nerve root. During examination, rotating the head and laterally bending toward the symptomatic side (Spurling’s test) exacerbates the arm pain. Routine neurologic examination reveals the changes characteristic of the involved nerve root, as discussed earlier (25) (11,12).

Very large herniated cervical disks may cause myelopathic symptoms. This may be seen in young patients who still have a large amount of material in their disks and a congenitally narrow canal. If the herniation is in the midline, the clinical presentation may demonstrate little if any arm pain but pure weakness and spasticity distal to the level of the blockage. Should the fragment be more to one side of the canal, radicular arm pain and lower motor neuron symptoms may be seen in addition to myelopathy at that level (13).

Patients with degenerative changes leading to cervical stenosis are the most common groups presenting with myelopathy. Degeneration of the intervertebral disk results in loss of height, annular bulge, and narrowing of the spinal canal. As the facets degenerate, the foramen and canal narrow and can deform the spinal cord and exiting nerve roots. Loss of disk height also allows infolding of the dorsal ligamentum, causing circumferential narrowing as the canal telescopes down. Instability can add further dynamic compression to a sensitive spinal cord. Preexisting congenital narrowing can lead to myeloradiculopathy at a much younger age than expected due to the usual aging process (4,6,14).

For the patient with advanced degenerative changes and a narrow spinal canal, a fall with hyperextension of the cervical spine is the classic cause of central cord syndrome. As the neck is forced into hyperextension during the traumatic episode, the cord is trapped between the osteophytes located at the dorsal aspect of the vertebral end plates and the infolding ligamentum flavum located dorsally (6).

Ossification of the posterior longitudinal ligament is seen most commonly in Asia, particularly in Japan; however, it is not unusual to see it in the United States. As the ligament is ossified with cortical bone, it continues to grow and occupy more space in the spinal canal. Over time, the cord may become quite compressed, and myelopathic symptoms may ensue. These patients have a fairly stiff spine, providing some protection of cord function because there is limited mechanical stimulation of the cord. Myelopathic symptoms may appear gradually, or they may appear with a traumatic incident. Men and women are affected equally. Because the compression of the cord is from cortical bone, it may be better seen by computed tomography (CT) than by MRI, which does not visualize lamellar bone as well (15,16).