Online Module: Spine Degenerative Disc Disease and Low Back Pain Herniated Nucleus Pulposus Cervical Spinal Stenosis Lumbar Spinal Stenosis

Degenerative Disc Disease and Low Back Pain

Degenerative Disc Disease (DJD) Unfortunately, DJD seems to be sort of a “wastebasket term” that is often used to describe age-related changes on MRI, etc. While these changes are indeed “degenerative,” this happens as we age and is not necessarily indicative of any significant underlying pathology or condition. The majority of individuals > 60 will show some type of degenerative change(s) on lumbar imaging.

DJD Degeneration of an individual disc space typically refers to loss of disc height, loss of water content, fibrosis, end plate sclerosis/defects, osteophyte complexes, etc.

Low Back Pain (LBP) LBP is extremely common; a majority of individuals will experience at least one episode of it in their life. ~85% of LBP is idiopathic, even with workup. Most patients with LBP improve on their own in time (even without treatment). Physical therapy and pain meds (even nonprescription such as NSAIDs) are appropriate mainstays of initial treatment.

Taking a history in a pt. with LBP Evaluation of patients with LBP should be geared towards identification of those patients with a potentially serious underlying etiology. Cancer Infection – osteomyelitis, abscess, etc. Fracture Cauda Equina Syndrome

Things that should raise a “red flag” Previous hx of cancer, unexplained weight loss Immunosuppression, hx of steroid use, hx of IV drug abuse, hx of skin/other infection(s) Hx of recent falls or trauma (including surgery) Bladder dysfunction (usually urinary retention or overflow incontinence) or fecal incontinence, “saddle anesthesia”, leg weakness Pain that doesn’t improve with rest; failure to improve after 4 weeks conservative management

Other things to check with LBP Social factors are important to ask about. Employment status Any pending litigation? Vitals can give clues (fever with infection, etc). Routine labs are usually sufficient. Good physical exam should pick up neurological compromise, if present. Palpation of the spine looking for tenderness, etc., also important (trauma, infection).

Radiography Currently, radiographic imaging is not recommended for patients with no “red flags” on history and physical if they have had symptoms less than 4 weeks duration. If red flags present, or persistent symptoms beyond 4 weeks, radiographic evaluation is recommended. Then referral as/if appropriate.

Herniated Nucleus Pulposus

Concept Intervertebral discs can be thought of, conceptually, kind of like a “jelly donut.” The outside is the annulus fibrosus, and the inside “jelly” is the more watery nucleus pulposus. Intervertebral discs act as shock absorbers between the vertebral bodies. Just like jelly donuts have a “weak spot” where the jelly squirts out if you squeeze them, the annulus of discs is weak posteriorly where the nucleus pulposus can herniate through, causing symptoms.

Presentation The classic presentation of Herniated Nucleus Pulposus (HNP), both for cervical and lumbar spine, is radiculopathy. The disc herniation impinges upon a nerve root, causing characteristic pain. Thoracic disc hernations are much, much rarer. Though it can cause myelopathy in the cervical spine (see Cervical Spinal Stenosis, later), Cauda Equina Syndrome in lumbar spine (see module), etc., other presentations won’t be discussed here.

Lumbar HNP “Sciatica” is the classic radiculopathy of lumbar HNP, though the exact presentation depends upon the nerve root(s) involved. Motor weakness can occur, which again is representative of the nerve root(s) involved. L4 – quadriceps (knee extension) L5 – tibialis anterior (foot dorsiflexion) S1 – gastrocnemius (foot plantar flexion) Lower Motor Neuron signs

Lumbar HNP 90% of herniated discs are paracentral (slightly off to one side) and affect the nerve root that corresponds to the lower vertebral level. Example: a typical L4/5 disc herniation would cause symptoms referrable to the L5 nerve root. As many as 10% of herniated discs, however, are “far lateral” and impinge upon the nerve root that corresponds to the upper vertebral level. A far lateral disc hernation at L4/5, then, would be expected to cause symptoms relative to the L4 root.

Lumbar HNP – when to operate The natural history of herniated discs is to resolve over time. If conservative management can adequately treat a patient’s pain, this is the preferred course of action. If conservative management fails to adequately control pain, surgery can be performed (often times on an outpatient basis).

Lumbar HNP Emergent surgery – only for new or progressive motor deficit, or Cauda Equina Syndrome. “Urgent” surgery sometimes for severe, incapacitating pain clearly referrable to a disc herniation that is not being adequately treated with pain meds/conservative management. Diagnostic modality of choice is non-contrast MRI. Can do myelogram in patients who can’t get MRI.

Cervical HNP Classic presentation is to “wake up with it.” Usually no identifiable factor. Causes painful limitation of neck motion and symptoms corresponding to the affected nerve root(s) The majority of cervical herniated discs will catch the nerve root corresponding to the lower vertebral level. Ex: A C6/7 disc herniation will impinge upon the C7 root.

Cervical HNP Just as is the case with Lumbar HNP, conservative therapy is the mainstay of treatment. Surgery indicated for those that don’t improve with conservative management, or with new/progressive neurologic deficit.

Cervical Spinal Stenosis

Cervical Spinal Stenosis (CSS) Stenosis – a constriction or narrowing of a duct or passage. Cervical spinal stenosis, thus, is narrowing of the spinal canal (within which lies the cervical spinal cord). This narrowing can be from any of a multitude of causes. Usually, though, this is referring to more chronic types of processes, rather than acute or sudden ones.

CSS More than half of adults older than 50 yrs. Will show significant degenerative cervical spine disease on radiography (CT/MRI)… (i.e., “Everybody has degenerative disc disease. And probably their dogs and cats too.” …however, only a fraction of these patients will actually experience any type of significant neurological symptoms.

CSS – when it causes problems… Radiculopathy – from nerve root compression. The term “radiculopathy” refers to disease of the nerve roots; LMN signs, pain/parasethesias. Myelopathy – from spinal cord compression. The term “myelopathy” refers to pathological changes of the spinal cord itself. Pain and sensory changes in the back of the head, neck, and shoulders.

CSS - Myelopathy The goal here is to avoid missing patients who are myelopathic, because once stenosis has evolved to the point that it is compressing (and causing damage to) the spinal cord, the progression of symptoms may be variable…but it is going to progress.

CSS myelopathy - History Some patients attribute weakness to “getting old,” and because they aren’t having neck pain (many myelopathic patients don’t), they don’t realize there’s a problem that needs addressing. Ask about fine motor movements, like buttoning buttons, tying shoes, signing checks, handwriting changes, using utensils, etc. “Clumsiness” with fine motor skills is common.

CSS myelopathy - Physical Exam Hyperactive reflexes are the most common physical exam finding in myelopathy. Remember the difference between Upper Motor Neuron and Lower Motor Neuron signs. Remember symmetry – a Hoffman’s on one side, if not on the other, should raise a red flag. Remember that a Babinski reflex, if present, is ALWAYS abnormal.

T2 weighted MRI, sagittal view; This patient has multilevel degenerative changes of the cervical spine. The bottom two arrows show mild stenosis with CSF (white, fluid signal) still flowing around the cord. However, the top arrow is pointing to the C3/4 level where there is severe cervical spinal stenosis, no CSF around the cord (compression), and signal change within the spinal cord itself (indicating damage).

Surgery The goal of surgery is to halt the progression of myelopathy through adequate decompression of the area(s) of stenosis. Once patients are clinically myelopathic, complete return of function and/or remission of symptoms almost never occurs. This is why they need to be identified early!

Clinical Pearl Future anesthesiologists take note: Blood Pressure is the spinal cord’s friend! If you run these patients hypotensive under anesthesia, they can wake up paralyzed! Hypotension can induce an ischemic event within the cord at the area of compression/stenosis. DON’T DO IT!

Lumbar Spinal Stenosis

Lumbar Spinal Stenosis (LSS) Just as we discussed with Cervical Spinal Stenosis, “Lumbar Spinal Stenosis” can occur secondary to anything which narrows the lumbar spinal canal, and it can occur in conjunction with other conditions/diseases. But when we mention it, we are usually referring to a chronic, degenerative process that causes spinal canal narrowing over time (i.e. “spine aging”).

Lumbar Spinal Stenosis Remember that the Spinal Cord ends at the Conus Medullaris, which is typically located at the L1/2 interspace in adults. L1/2 is the lumbar level least likely to be affected by Lumbar Spinal Stenosis. Thus, Lumbar Spinal Stenosis doesn’t cause myelopathy; when it affects the motor system, lower motor neuron signs are what you’ll find.

LSS - presentation The “classic” presentation of Lumbar Spinal Stenosis is Neurogenic Claudication (NC), or “pseudoclaudication.” (~60% sensitivity, but >90% specificity). Gradually progressive back, thigh, buttock, and/or leg pain that is relieved by rest and/or, characteristically, a change in posture; usually through flexion at the hips (sitting or squatting, etc.).

Neurogenic Claudication Neurogenic Claudication is thought to arise from compression of, irritation to, or ischemia of the lumbosacral nerve roots. This is in contrast to Vascular Claudication (VC), which is secondary to insufficiency of vascular supply to meet demand of muscles (pain is ischemic, but from muscles). Differentiating between the two isn’t always easy, but you should understand the difference!

Vascular Lab Studies may help differentiate between NC and VC “Anthropoid posture” (walking bent-over as though they’re pushing a shopping cart) is common in NC, and pain may be reproduced with lumbar extension. Vascular Lab Studies may help differentiate between NC and VC Ankle-Brachial Index (ABI) Ultrasound Table 14-18 adapted from Greenberg’s Handbook of Neurosurgery, 6th ed.

Management Unless there is severe neurological deficit, conservative medical management is usually tried prior to pursuing surgery. Pain meds, epidural steroid injections, etc. If medical management is unsuccessful, surgery for Lumbar Spinal Stenosis is aimed at removing the bony lamina and soft tissue elements that are contributing to the canal stenosis.