Diseases of the Spinal Nerve Roots and Peripheral Nerves

diminished biceps reflex

diminished or absent biceps reflex

diminished or absent triceps reflex

diminished triceps reflex

weakness of quadriceps (knee-jerk) reflex

weakness of quadriceps reflex

absent tibialis posterior reflex (of diagnostic value only when clearly elicitable on opposite, unaffected side)

absent gastrocnemius reflex (ankle-jerk or Achilles reflex)

triceps reflex key to differential diagnosis vs. carpal tunnel syndrome

triceps reflex key to differential diagnosis vs. ulnar nerve palsy

differential diagnosis vs. femoral nerve palsy: sensation intact in distribution of saphenous n.

differential diagnosis vs. femoral nerve palsy: involvement of tibialis anterior m.

differential diagnosis vs. peroneal nerve palsy: in the latter, tibialis posterior and hip abduction are preserved

Lumbar Disk Herniation

Lumbar disk herniation is one of the more common causes of acute low back pain and sciatica. The anatomical relationship of the lumbar roots to the intervertebral disks (both normal and herniated) is shown schematically in Fig. 12.5.

Clinical manifestations. A first bout of lumbar disk herniation (and often the first or second recurrence as well) may present with no more than acute low back pain (lumbago). The event may be precipitated by a relatively banal movement in the wrong direction; in particular, the lumbar spine may suddenly freeze in a twisted position as the unfortunate individual attempts to lift a heavy load while the upper body is turned to one side. Any further movement of the lumbar spine is blocked by muscle spasm, a reflex response to the pain. Even the smallest movement is painful, as are coughing and abdominal pressing (Valsalva maneuvers). The pain usually resolves after a few days of bed rest. It is usually only when the herniation recurs later that the patient experiences pain radiating into the leg, i. e., sciatica, and possibly in combination with typical radicular neurological deficits.

In our experience, motor deficits generally arise only later in the course of this syndrome. The patient must be examined carefully to determine whether a deficit is present. The L5 root is most commonly affected, usually by an L4−5 disk herniation, and the S1 root is the next most commonly affected after that, usually by an L5−S1 disk herniation. The corresponding clinical findings are listed in Table 12.1.

Diagnostic evaluation. As in cervical disk herniation, the level of the nerve root that is affected can generally be determined from the pattern of referred pain and any motor, sensory, and reflex deficits that may be present. The peripheral nerve trunk containing the axons whose more proximal portions are located in the affected root is often sensitive to pressure (at the Valleix pressure points) and stretching of the nerve is often painful. The latter can be tested by passive raising of the supine patient’s leg, extended at the knee (the Lasègue test). Pain caused by elevation of the leg on the side opposite the sciatica (the crossed Lasègue sign) usually indicates a large, prolapsed disk herniation. If a higher lumbar root (L3 or L4) is affected, one should look for the reverse Lasègue sign, i. e., test for pain on extension of the leg in the prone patient, which stretches the femoral n. rather than the sciatic n. (reverse Lasègue test). If the herniation is lateral or extraforaminal, pain will also be inducible by lateral bending of the trunk.

Imaging studies are not absolutely essential if the clinical picture is sufficiently characteristic, but they should be performed if there is any doubt as to the etiology of nerve root compression, or if the situation requires operative intervention. CT is the method of choice if the segmental level of the suspected disk herniation is clinically unambiguous; the main advantage of CT is that it can clearly demonstrate a far lateral disk herniation, if this turns out to be present (Fig. 12.6). It can also reveal bony deformities of the spinal canal and nerve root impingement by spondylotic changes, if present

Fig. 12.4 Spurling cervical compression test for the provocation of radicular pain in cervical disk herniation (after Mumenthaler M.: Der Schulter−Arm−Schmerz, 2nd edn, Huber, Bern 1982.) Pain can often be elicited by reclination and rotation of the head toward the affected side even without compression.

(Fig. 12.7). MRI is to be preferred over CT, however, if the level of the lesion is not fully clear on clinical grounds. The images should always be interpreted critically and in consideration of the associated clinical findings.

Neurography and electromyography are sometimes worth performing as supplementary tests.

Treatment. The initial treatment is conservative in practically all patients and is along the same lines as described above for cervical disk herniation. Operative treatment should be considered only if conservative treatment fails.

An incipient cauda equina syndrome (bladder and bowel dysfunction, saddle hypesthesia, bilateral pareses, and impairment of the anal reflex, cf. p. 144) is an absolute indication for urgent surgery.

!When the clinical signs of cauda equina syndrome are present because of lumbar intervertebral disk herniation, an emergency neurosurgical procedure must be performed immediately.

Further indications for operative treatment are set forth in Fig. 12.8. At operation, the herniated disk tissue is removed, and, if there is a danger of postoperative instability at the level being operated on, a fusion (spondylodesis) is performed as well. This is more likely to be the

case in older patients and when the intervertebral disk degeneration is very advanced. As in cervical disk procedures, spondylodesis must be performed in such a way as to keep the vertebral bodies above and below the disk a sufficient distance apart (in distraction), so that the intervertebral foramina are held open.

Radicular Syndromes Due to

Spinal Stenosis

Slowly progressive mechanical compression of the intraspinal neural structures is usually seen in older patients in whom congenital narrowness of spinal canal has been accentuated by further, progressive, degenerative osteochondrotic and reactive-spondylogenic changes.

Cervical Spinal Stenosis

A narrow cervical spinal canal can compress not only the cervical nerve roots, but also the spinal cord itself, producing a myelopathy. Cervical spondylogenic myelopathy is discussed in detail above on p. 147.

Lumbar Spinal Stenosis

For anatomical reasons, a narrow lumbar spinal canal causes an entirely different clinical syndrome than cervical spinal stenosis:

Clinical manifestations. In addition to low back pain, which is usually chronic, neurogenic intermittent claudication is the most characteristic symptom: as the patient walks, sciatica-like pain arises on the posterior aspect of one or, usually, both lower limbs and then becomes progressively severe. The pain appears earlier if the patient is walking downhill, because of the additional lumbar lordosis that downhill walking induces. This historical feature differentiates neurogenic from vasogenic intermittent claudication, in which the pain tends to be more severe when the patient walks uphill. A further differentiating feature of neurogenic, as opposed to vasogenic, intermittent claudication is that standing still will not, by itself, cause the pain to go away. The patient must additionally bend forward, sit down, or crouch—these maneuvers induce kyphosis of the lumbar spine and thereby decompress its neural contents.

Diagnostic evaluation. Nowadays, the definitive diagnostic study is MRI, though radiculography and myelographic CT are still sometimes needed (Fig. 12.9).

primary tumor, while ependymoma (Fig. 12.11), glioma (usually astrocytoma), and vascular tumors are rarer. Nerve root lesions can also be caused by a primary destructive process affecting a spinal vertebra (Fig. 12.12), particularly metastatic carcinoma. Finally, infectious and inflammatory processes of the vertebrae and intervertebral disks (e. g., spondylodiscitis), as well as spinal abscesses and empyema, can cause radicular or spinal cord compression.

Clinical manifestations. The patient usually complains of pain radiating into the periphery; if the lesion is at a thoracic level, the pain tends to be in a bandlike distribution around the chest. Motor or sensory deficits may also be clinically detectable, depending on the level of the lesion. A space-occupying lesion within the lower lumbar canal can produce cauda equina syndrome, which may be of greater or lesser severity.

Diagnostic evaluation. Imaging studies are indispensable for diagnosis. If the underlying lesion is a nerve root neurinoma, plain films may already reveal the characteristic, widened intervertebral foramen, e. g., in the cervical region (Fig. 12.13). Nonetheless, CT or MRI (Fig. 12.14) is always necessary to demonstrate the full extent of the tumor.

Treatment. Operative treatment (resection of the lesion) is needed in most patients. Depending on the underlying illness, further treatment may be required (radiotherapy, antineoplastic chemotherapy, or antibiotics after the removal of an abscess or empyema).

Fig. 12.11 Sausage-shaped cystic ependymoma filling the spinal canal from L1 to L3 and compressing the cauda equina (MR image).

a

Fig. 12.12 Metastatic melanoma in the lumbosacral spinal canal, 8 years after resection of the primary tumor: sagittal (a) and axial (b) MR images. The patient presented with cauda equina syndrome.

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b

The nerve roots of the cauda equina are displaced dorsally and to the left by the compressive lesion.