Cervical Degenerative Conditions

Yu-Po Lee, MD

Saif Aldeen Farhan, MD

Nitin Bhatia, MD

Dr. Lee or an immediate family member serves as a paid consultant to or is an employee of DePuy, A Johnson & Johnson Company. Dr. Bhatia or an immediate family member has received royalties from Alphatec Spine, Biomet, Seaspine, Spineart, and Stryker; is a member of a speakers’ bureau or has made paid presentations on behalf of Alphatec Spine, Biomet, Seaspine, Spineart, and Stryker; serves as a paid consultant to or is an employee of Alphatec Spine, Biomet, DiFusion, Seaspine, Spineart, Zimmer, and Stryker; has stock or stock options held in DiFusion; and serves as a board member, owner, officer, or committee member of the Cervical Spine Research Society, the North American Spine Society, and the Western Orthopaedic Association. Neither Dr. Farhan nor any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this chapter.

ABSTRACT

Degenerative disorders of the spine can present as a spectrum of disorders. In its mildest form degeneration of the cervical disks can cause mild neck pain and stiffness. However, advanced progression of the degenerative process can result in nerve root and spinal cord injury. Degeneration of the cervical spine can also lead to deformity of the cervical spine with spinal cord and nerve root impingement. The ability to recognize key signs and symptoms of progressive cervical degeneration and how to differentiate between the various ways that it can present is essential for physicians and surgeons who treat patients with cervical disorders.

This chapter will describe the evaluation and management of cervical degenerative disorders.

Keywords: cervical deformity; cervical spondylosis; cervical spondylotic myelopathy; cervical stenosis

Introduction

Degenerative disorders of the spine can present as a spectrum of disorders. In its mildest form degeneration of the cervical disks can cause mild neck pain and stiffness, although it frequently is asymptomatic.¹^,²^,³ As the degenerative process advances, degeneration of the disks leads to protrusion of the disks and osteophyte formation. Bulging of the disks and osteophyte formation can compress the nerves and spinal cord and lead to pain and loss of function. This spinal degenerative process is also called spondylosis. Dysfunction of the nerve roots due to nerve root compression is termed radiculopathy, and dysfunction of the spinal cord due to spinal cord compression is termed myelopathy. Cervical spondylosis is the most common cause of cervical myelopathy in people aged 55 years and older, and the disorder is termed cervical spondylotic myelopathy (CSM).⁴ The rate and degree of neurologic deterioration are variable. Early recognition and treatment of CSM is critical before the onset of spinal cord damage.

Cervical disk herniations can also be a source of severe pain and disability.¹^,²^,³ As the disk degenerates, a fragment of the nucleus pulposus or anulus fibrosus can break off and herniate into the canal. This can lead to symptoms of radiculopathy or myelopathy depending on if the disk compresses the nerve roots or spinal cord, respectively. At the end of the spectrum of cervical degenerative disorders is cervical deformity. This can present as cervical kyphosis (sagittal plane deformity) or scoliosis (coronal plane deformity). Progressive degeneration of the disks and weakening of the muscles and soft tissues leads to deformity of the cervical spine with spinal cord and nerve root impingement.

This chapter will describe the evaluation and management of cervical degenerative disorders.

Evaluation

Evaluation of cervical degenerative disorders starts with a careful history and physical examination. Questions that may provide clues to the cause of a patient’s
symptoms include whether the patient has pain, loss of sensation, or weakness.⁵^,⁶^,⁷ The primary location of the symptoms is also important. Is the pain in the neck or does it radiate into their arms? Is there a loss of sensation and loss of coordination in the hands or is there any difficulty with balance and gait? Important factors include when the symptoms occurred, how long the symptoms were present, and if there was antecedent trauma. Other factors include if the symptoms have improved or worsened over time or if they have waxed and waned over time. Also, it is important to consider factors that alleviate and exacerbate the symptoms. Asking these questions can help in formulating a differential diagnosis.

Patients with disk degeneration may complain of axial neck pain. The pain will often be chronic and insidious in nature. Sometimes there is an inciting event that worsens their pain. The neurologic examination will be benign in most cases. Patients with a cervical disk herniation, however, will complain of a sudden and acute pain that is very intense. Depending on the level of the herniation they will have loss of sensation and motor weakness in a distribution that is consistent with the nerve root affected.

Myelopathy presents with a variety of subtle neurologic findings.⁵^,⁶^,⁷ Characteristic signs and symptoms can present insidiously and include the loss of manual dexterity in the hands, weakness, stiffness, urinary symptoms, spasticity in their extremities, and gait disturbance including a stiff or spastic gait. Patients demonstrate a wide-based gait and report a history of loss of balance and falls. Sensory findings often include proprioceptive loss, and patients may report that they have difficulty with buttons, a change in their handwriting, or that they are dropping objects.

A comprehensive neurologic examination should be performed. The motor examination may be completely normal even in cases of nerve root or spinal cord compression. When upper extremity weakness is present, it often presents as diminished grip and/or intrinsic strength. The finding of severe weakness of major muscle groups in the upper or lower extremities is relatively uncommon. Sensory examination should also be performed, but the findings are often subtle. The neurologic examination should include an assessment for gait instability. Hyperreflexia may be present in the upper and/or lower extremities and is suggestive of spinal cord compression with upper motor neuron signs. These findings, however, can be masked or diminished in patients who have concomitant diabetes mellitus, peripheral neuropathy, or lumbar stenosis.

Spinal cord compression with myelopathy can manifest with abnormal upper motor neuron signs such as Hoffman’s sign, inverted radial reflex, pathological clonus, and Babinski’s sign.⁵^,⁶^,⁷ The Hoffman’s sign is described as quick flexion of both the thumb and index finger when the middle finger nail is snapped. Clonus is a series of abnormal reflex movements of the foot in plantar flexion, induced by sudden dorsiflexion. This finding is caused by alternate contraction and relaxation of the triceps surae muscle. The number of times the foot contracts in plantar flexion is recorded and may be a sign of spinal cord pathology. The Babinski reflex occurs after the sole of the foot has been firmly stroked. The big toe then moves upward or toward the top surface of the foot while the other toes fan out. The inverted radial reflex is noted by flexion of the fingers without flexion of the forearm when the distal end of the radius is tapped. Lhermitte’s sign is an electric shock-like sensation that runs down the center of the patient’s back and enters the limbs during flexion of the neck.

Myelopathy can often be accompanied by radicular findings in some patients. Myeloradiculopathy is associated with spinal stenosis with concurrent compression of the neuroforaminal contents, which produces lower motor neuron signs at the level of the cervical cord lesion and upper motor neuron signs caudal to the level of compression.

Differential Diagnosis

Once a careful history and physical examination have been performed, the surgeon can then start to formulate a differential diagnosis. There are many conditions that affect the central and peripheral nervous system that can mimic the signs and symptoms of cervical degenerative disorders. Some pathologies to include in the differential are a central nervous system disorders, demyelinating processes such a multiple sclerosis and transverse myelitis, stroke, tumor, trauma, infection, peripheral nerve compression disorders, nutritional myelopathy such as a vitamin B₁₂ deficiency, and even shoulder pathology.⁸^,⁹

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder that can be difficult to recognize because of overlapping demographics and clinical symptoms with cervical degenerative disorders. ALS can present with upper and lower motor neuron deficits, as well as cranial nerve deficits. An electromyography study (EMG) demonstrating a denervation pattern can serve as diagnostic evidence for ALS, although a muscle biopsy may be necessary during the diagnostic process. Guillain-Barré syndrome can present with a subacute onset of progressive weakness. This disorder
occurs when the immune system attacks the peripheral nervous system. Multiple sclerosis is a demyelinating disorder that can cause progressive loss of sensation and weakness. While the cause is unclear, the underlying mechanism is thought to be either destruction by the immune system or failure of the myelin-producing cells. Gait and bladder dysfunction can be found in patients with normal pressure hydrocephalus. Additional cranial nerve abnormalities and/or a hyperactive jaw jerk reflex would suggest the presence of a brain stem or intracranial lesion. Cognitive dysfunction can help differentiate between normal pressure hydrocephalus and other central nervous disorders from CSM.

Peripheral nerve compression disorders should also be included in the differential diagnosis. Patients should be screened for possible carpal tunnel syndrome, cubital tunnel syndrome, and thoracic outlet syndrome if their signs and symptoms suggest such diagnoses. It is not uncommon for patients to have nerve compression in their spinal canal and at a distant site. This dual compression is called a double crush syndrome. Patients with rotator cuff tears and other shoulder pathology may also present with symptoms mimicking cervical degeneration, although examination of the shoulder may provide insight as to the underlying pathology.

Imaging

Plain radiographs are commonly used as the initial imaging of the spine as they are relatively inexpensive and easy to obtain. Radiographs can provide useful information regarding the specific location and severity of spinal degeneration. Spinal cord and/or nerve root impingement may be suspected if the clinical history and physical examination correlate with affected degenerated levels seen on radiographs. Radiographs can also show instability and deformity. Routine radiographs often include AP and lateral radiographs as well as flexion-extension views.

To confirm spinal cord compression, advanced imaging using MRI or CT myelography is preferred. MRI is noninvasive and provides visualization of the intervertebral disks, spinal cord, and nerve roots. MRI also provides good visualization of spinal cord and nerve root compression. Signal changes within the spinal cord seen on MRI are suggestive of severe compression and spinal cord injury.¹⁰ Signal changes seen on T1- and T2- weighted MRI imaging of the spinal cord have also shown a moderate ability to predict outcomes after surgical intervention (Figure 1). In general, T2 weak signal hyperintensity (more intense than normal spinal cord but less intense than CSF) that appears diffuse without clear bordering has been associated with potentially reversible changes such as edema, Wallerian degeneration, demyelination, and ischemia. T2 imaging showing substantial hyperintensity with sharp bordering and T1 hypointensity represent changes considered to be irreversible such as cavitation, neural tissue loss, myelomalacia, necrosis, and spongiform changes in gray matter. In addition, myelopathic signs as discussed previously have been shown to be significantly more common in patients with cord signal changes suggestive of myelomalacia.

Figure 1 T2-weighted image showing severe central canal stenosis with myelomalacia.

If a patient cannot undergo MRI for medical reasons (such as the presence of cardiac pacemakers, aneurysm clips, or claustrophobia), or if metal or scar tissue from prior cervical surgery obscures visualization on MRI because of artifact, CT myelography is a good alternative. Plain CT is also a good adjunct to MRI in some cases. For example, a CT scan can be helpful if OPLL (ossification of posterior longitudinal ligament) (Figure 2, A and B) is suspected or to better visualize the vertebral artery if a corpectomy or C2 pedicle screws are planned.

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