Spondylotic and Other Structural Myelopathies (Spinal Cord Disorders February 2021)

Educational Objectives

The goal of this program is to improve management of spinal cord disorders. After hearing and assimilating this program, the clinician will be better able to:

1. Assess the significance of radiographic findings in a patient with worsening symptoms of cervical spondylotic myelopathy.

2. Recognize early and late signs and symptoms of cervical spondylotic myelopathy.

3. Provide patients with effective options for treatment of syringomyelia and its follow-up.

Summary

Definition and diagnosis of myelopathy: Myelopathy refers to a disorder of the spinal cord; the disease and its symptoms are related to specific lesions in the spinal cord; the diagnosis is clinical and involves the correlation of symptoms and signs with findings on imaging.

Role of the neurologist in management of myelopathy: The initial role is to identify the cause, because symptoms can be similar in myelopathies with different causes (eg, symptoms of myelopathies caused by cervical spondylosis and those caused by deficiency of vitamin B12); misdiagnosis can lead to errors and need for significant changes in therapy; other roles include performing serial examinations (eg, when intervention is not an option but may be necessary in the future) and managing symptoms.

Cervical Spondylotic Myelopathy

Consequences of a missed diagnosis: The prevalence of cervical spondylotic myelopathy is high; its diagnosis may be complicated, because it cannot be confirmed by a single test; MRI of the cervical spine is often performed, but findings on imaging (eg, degree of stenosis, indentation of the spinal cord, narrowing of the space for CSF around the spinal cord) are not well correlated with neurologic symptoms; in the United States, the leading causes of nontraumatic injury to the spinal cord are structural; patients may undergo unnecessary surgery because findings of imaging of the cervical spine do not correlate with the cause of their symptoms (eg, patients who have Parkinson disease).

Factors in susceptibility to clinical disease: Include osteoarthritis and other degenerative diseases, inflammatory disease (eg, rheumatoid arthritis, ankylosing spondylitis), genetic syndromes (eg, Down syndrome), and congenital spinal stenosis.

Radiographic criteria for diagnosis of congenital spinal stenosis: An anteroposterior diameter of the spinal canal of 13 mm or less on a sagittal view of MRI is a commonly accepted criterion; however, according to some clinicians, the numeric cutoff depends on the habitus and physiology of the patient and the proportion of the canal occupied by the spinal cord; in an alternate definition, the canal is congenitally narrow if the spinal cord occupies more than 70%; in patients suspected of having cervical spondylotic disease, evaluation should be performed where bony alignment appears relatively normal (rather than at the portion with disease), and the fractional occupancy ratio of adjacent segments should be determined.

Relationship between narrowing of the spinal canal and symptoms: The presence of a narrow canal alone is not diagnostic; an experimental study in dogs found that running and movement were initially normal after narrowing of the canal; however, progressive signs of disease developed after a mean of 7 months; in humans, wide variability in degree of stenosis and development of clinical disease is found; neurologic symptoms may fluctuate while the degree of stenosis on imaging remains constant.

Causes of symptoms: Repetitive microtrauma may cause flexion-extension injury to the spinal cord and explain the gradual progression of myelopathy; the anterior horn is the most common site of injury; the end-arterial zone at this site is supplied by the anterior spinal artery and develops microischemia with flexion-extension trauma to the spinal cord; neuroinflammation has been found in pathologic samples from stenotic areas of the spinal cord; disease processes other than mechanical compression of the spinal cord likely account for variability in clinical course and treatment.

Clinical signs and symptoms: Chronic disease is more common than acute disease; in the early stages of chronic disease, gait disorder (a stiff uncertain gait) is the predominant feature and is often missed; over time, numbness, tingling, and weakness or lack of manual dexterity of the hands may be present; dysfunction of the bowel or bladder typically is not an early symptom; onset of symptoms is often acute when an injury (eg, a fall down stairs) is superimposed on preexisting stenosis; these patients often develop a central cord syndrome characterized by weakness in the arms and dysfunction of the bowel or bladder.

Findings of examination: In chronic cervical spondylotic myelopathy, typical findings include mild spasticity in the legs, hyperreflexia (often asymmetric), and unexplained minimal weakness of the hands; in older patients who report gait ­instability but have brisk reflexes in the lower limbs, disease of the cervical spine should be considered; sensitivity for early disease is greater for the Hoffman sign than the Babinski sign.

Imaging: If the level of suspicion for cervical spondylotic myelopathy is high, MRI is recommended first; although CT may reveal bony disease, it often misses diskogenic or ligamentous changes that are important in assessing the degree of stenosis; the sensitivity of findings of x-ray evaluation is low; however, x-ray examination performed with the patient in flexion and extension may reveal dynamic instability of the bones not revealed on MRI; MRI is recommended when a high clinical index of suspicion is present.

Predictors of benefit from surgery: T2 changes in the spinal cord on MRI are not predictive for outcome after surgery; a bright T2 change (the same intensity as cervical CSF) with hypointensity on the T1 sequence reveals gliosis that may not be reversible with surgery; patients who have myelomalacia with long clinical stability may not benefit from surgical intervention.

Syringomyelia

Differential diagnosis: Hydromyelia is often an incidental finding; it is characterized by an enlarged central canal lined with ependymal cells; syringomyelia is characterized by a fluid-filled cavity (syrinx) lined with glial cells; hydromyelia is typically found at the junction of the anterior one-third and posterior two-thirds of the spinal cord, is circular, and does not cause myelomalacia of the surrounding spinal cord; of patients undergoing spinal imaging, approximately 1% to 2% are found to have an enlarged central canal that does not increase in size over time; in syringomyelia, the cavity may be static or expand and interrupt crossing and descending fibers; patients are often more symptomatic than those with hydromyelia.

Causes: Malformation is a common cause; however, the process by which downward herniation of the cerebellum into the foramen magnum causes fluid to build up in the spinal cord is unclear; hydrodynamic theories focus on the aberration of free flow of CSF around the spinal cord.

Treatment: Often centers on managing the interruption of CSF flow; many patients do not require treatment; a large mismatch between clinical and radiographic findings is often present; considerations in choosing treatment include the presence and progression of symptoms and interventions that might be implemented; the most favorable outcomes are found in patients with mild symptoms that are just beginning to progress and a clear lesion in which decompression can be performed (eg, Chiari malformation) to normalize the flow of CSF and lead to stabilization or resolution of the syrinx.

Recommendations for follow-up: Focus on clinical assessments, because findings on imaging may not change rapidly; therefore, detailed examination is important; for patients who have stable disease, imaging is typically performed every 1 to 2 years with clinical follow-up every 6 months.

Cervical Spondylotic Myelopathy (Continued)

Indicators of progression associated with occupational exposure: Worsening symptoms or increased weakness at the end of the day after extension of the neck suggests that activities are exacerbating the syndrome (this idea is not supported by data); according to anecdotal reports, jobs in the construction industry that involve the use of jackhammers or continuous vibration of the cervical spine may increase risk for progression; however, evidence is insufficient to support the need to discontinue this work; in patients who have severe cervical spondylotic stenosis on imaging but who are asymptomatic, minor trauma (eg, hitting the head on a doorway) is unlikely to lead to paralysis.

Take-home Messages

Evaluation of patients: In patients who have acute, subacute, or progressive myelopathy, the differential diagnosis should include structural disease of the spine; the spectrum of clinical presentations should be considered; significant mismatch between clinical and radiologic findings is typically found; therefore, sequential neurologic examinations and assessment for alternate causes are key components of diagnosis and management; abnormalities of the spine or arachnoid space can affect the spinal cord directly or indirectly and provide clues to idiopathic causes of progressive myelopathy.

Multidisciplinary approach: The recommended strategy; it should include a neurologist, neuroradiologist, orthopedic surgeon, neurosurgeon, physical rehabilitation specialist, and physical therapist.

Readings

Spondylotic and Other Structural Myelopathies

Bhattacharyya R. Spondylotic and other structural myelopathies. Continuum (Minneap Minn) 2021;27(1, Spinal Cord Disorders).

Disclosures

For this program, the following was disclosed: Dr. Bhattacharyya has served as a consultant for Alexion Pharmaceuticals, Inc, and has received personal compensation for providing second opinion service for Teladoc Health, Inc. Dr. Bhattacharyya receives publishing royalties from Springer and UpToDate, Inc.

Unlabeled Use of Products/Investigational Use Disclosure: Dr. Bhattacharyya reports no disclosure.

To view disclosures of planning committee members with relevant financial relationships, visit: legacy.audio-digest.org/continuumaudio/committee. All other members of the planning committee report nothing to disclose.

The material presented in Continuum Audio has been made available by the AAN for educational purposes only and is not intended to represent the only method or procedure for the medical situations discussed but rather to present an approach, view, statement, or opinion of the speaker(s), which may be helpful to others who face similar situations. Opinions expressed by the speakers are not necessarily those of the AAN, its affiliates, or the publisher. The AAN, its affiliates, and the publisher disclaim any liability to any party for the accuracy, completeness, efficacy, or availability of the material contained in this program (including drug dosages) or for any damages arising out of the use or nonuse of any of the material contained in this program.

Acknowledgements

CME/CE INFO

Accreditation:

The Audio- Digest Foundation is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.

The Audio- Digest Foundation designates this enduring material for a maximum of 0 AMA PRA Category 1 Credits™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

Audio Digest Foundation is accredited as a provider of continuing nursing education by the American Nurses Credentialing Center's (ANCC's) Commission on Accreditation. Audio Digest Foundation designates this activity for 0 CE contact hours.

Lecture ID:

CA100107

Expiration:

This CME course qualifies for AMA PRA Category 1 Credits™ for 3 years from the date of publication.

Instructions:

To earn CME/CE credit for this course, you must complete all the following components in the order recommended: (1) Review introductory course content, including Educational Objectives and Faculty/Planner Disclosures; (2) Listen to the audio program and review accompanying learning materials; (3) Complete posttest (only after completing Step 2) and earn a passing score of at least 80%. Taking the course Pretest and completing the Evaluation Survey are strongly recommended (but not mandatory) components of completing this CME/CE course.

Estimated time to complete this CME/CE course:

Approximately 2x the length of the recorded lecture to account for time spent studying accompanying learning materials and completing tests.