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Abstracts

Is cervical myelopathy overlooked in patients with fibromyalgia?

Dan S Heffez MD, Ruth E Ross PhD, Von Shade-Zeldow PhD, Konstantino Kostas PhD, Sagar Shah BS, Robert Gottschalk ND/FNP, Dean Elias MD, Alan Shepard MD, Sue E Leurgans PhD, Charity Moore PhD

Fibromyalgia is a syndrome characterized by diffuse chronic pain. The American College of Rheumatology has established diagnostic criteria, which have been helpful in distinguishing fibromyalgia from other chronic pain states but have not advanced the understanding of its etiology. The worldwide prevalence of fibromyalgia is estimated to be 2%. An estimated six million Americans are affected. In addition to the widespread pain, patients complain of a variety of symptoms, including overwhelming fatigue exacerbated by exertion, headache, dizziness, cognitive difficulties, instability of gait, limb numbness and paresthesiae. Some physicians have come to view the syndrome as a somatization disorder because of these numerous and apparently unrelated complaints, and because fibromyalgia fails to fit the biomedical cause-effect model.
Many of the symptoms reported by fibromyalgia patients are identical to those reported by patients diagnosed with either Chiari 1 malformation or with cervical myelopathy due to spinal stenosis, (spondylotic cervical myelopathy), two well-defined neurological disorders. Therefore, we evaluated a cohort of patients who carried the diagnosis of fibromyalgia for objective evidence of cervical myelopathy.

Two hundred and seventy (270) consecutive patients who carried the diagnosis of fibromyalgia were evaluated between September 1998 and May 2001. The sole requirement for referral was that the patient carry the diagnosis of fibromyalgia.
On initial evaluation, patients completed a questionnaire detailing their symptoms, current medications and past medical consultations. A diagram depicting the distribution of the patient's body pain and an analogue pain severity scale were completed. Patients were evaluated by a neurologist and/or a neurosurgeon who, independently of each other, performed a neurological examination and recorded the findings on a standardized form in order to insure that every patient was evaluated in the same manner. All data including the results of the examinations were entered into a relational database.

Every patient underwent magnetic resonance imaging of the brain with special attention to the foramen magnum in order to exclude a Chiari 1 malformation. For the purpose of determining the position of the cerebellar tonsils the lower lip of the foramen magnum was defined as extending from the lowest cortical bone of the clivus anteriorly (basion) to the lowest cortical bone at the opistion posteriorly on the mid sagittal MRI image. The position of the most caudal point of the tonsil(s) relative to the inferior lip of the foramen magnum was measured from the midsagittal MRI slice. MRI scan of the cervical spine was performed in order to identify any intrinsic spinal cord lesion capable of causing myelopathy.

Every patient also underwent computed tomographic (CT) imaging of the cervical spine following the intravenous infusion of 150 ml of non-ionic contrast (300mg of iodine/ml). The CT scan was performed with the patient's neck in the neutral and then in the extended position. The gantry angle was altered to obtain images perpendicular to the spine at each level. The mid-sagittal antero-posterior (AP) dimension of the spinal canal was determined at the level of the intervertebral disc space on both neutral CT and MRI images and on CT images with the neck extended.

MRI and CT images were individually scanned into a Pentium III personal computer using a Umax power look III scanner. One of two independent observers, unrelated to the medical evaluation or treatment of the patients, made measurements of the position of the cerebellar tonsils and the mid-sagittal AP spinal canal diameters using SigmaScan Pro software, version 5.0.

Eighty-six percent of the patients were women. Ninety-seven percent were Caucasian. The mean age was 44 years (SD=11 years). The mean duration of symptoms was 8 years (std dev 6.3 yrs). Fifty-nine percent of patients reported antecedent craniospinal trauma within 3-6 months of the onset of symptoms. On average, the patients had consulted 10 different medical specialists during the course of their illness. Patients were taking a mean of 4.8 medications, (including but not limited to opiate and non-opiate analgesics, benzodiazepines, antidepressants, sedative hypnotics and muscle relaxants), for the relief of symptoms related to fibromyalgia. Forty-one percent of patients had at least a college education. Sixty-eight percent of patients had left their job as a direct result of their illness.

The predominant complaints were neck/back pain (95%), fatigue (95%), exertional fatigue (96%), cognitive impairment (92%), instability of gait (85%), subjective grip weakness (83%), paresthesiae (80%), dizziness (71%) and numbness of the hands/feet (69%). Eighty-eight percent of patients reported worsening symptoms with neck extension.

The findings on neurological examination were diagnostic of cervical myelopathy. An upper thoracic spinothalamic sensory level (T3-T6) was noted in 83% of patients. Typically, we detected hyperalgesia and allodynia to a cold or lightly applied pinprick stimulus below a dermatome level. Rarely, a suspended band of hypesthesia to cold or pinprick stimulus was detected between the third and seventh thoracic dermatomes. The second most common neurological finding, (noted in 64% of patients), was hyper-reflexia. Recruitment, (the pathological spread of reflexes beyond the muscle being tested), including inversion of the radial periosteal reflex was observed in 57% of patients. Other objective neurological findings included positive Romberg sign (28%), varying degrees of ankle clonus (25%), positive Hoffman sign (26%), impaired tandem walk (23%), dysmetria (15%) and disdiadochokinesia (13%). The patients were examined first with the neck in the neutral and subsequently in the flexed and then in the extended positions. Neck extension and neck flexion resulted in immediate accentuation of abnormal pyramidal track findings in 88% and 73% of patients respectively, suggesting a mechanical etiology for the abnormal neurological findings.
The MRI images of the brain did not show any consistent intrinsic disease of the brain parenchyma. The only consistent finding was the caudal displacement of the cerebellar tonsils. The mean position of the cerebellar tonsils as measured on the mid sagittal MRI image was 1.1 mm (SD=4.4mm) below the rim of the foramen magnum. In 38% of patients the tonsillar herniation exceeded 3mm, (mean 5.6, SD=2.1 mm). In 20% of patients tonsillar ectopia exceeded 5 mm (mean=7.1, SD=1.8mm).
MRI and contrast enhanced CT imaging of the cervical spine revealed a narrow spinal canal, i.e. stenosis. The mean AP spinal canal diameter at C2/3, C3/4, C4/5, C5/6, C6/7 and C7T1 was 13.2, 11.7, 11.8, 10.7, 11.5 and 14.9 mm respectively, (CT images). In 23% of patients, the AP mid-sagittal spinal canal diameter was 10mm or less at the C5/6 intervertebral disc space as measured on CT or MRI images. The AP mid-sagittal spinal canal diameter at the level of the C5/6 intervertebral disc space measured 10mm or less in 46% of patients when the neck was positioned in extension, (CT images). MR imaging of the cervical spine did not reveal any consistent intrinsic spinal cord disease with the exception of signal hyper-intensity at the level of spondylotic spinal cord compression noted on the T2 sequence images in some patients.

Symptoms of myelopathy are variable and can be quite vague, often leading to initial misdiagnosis. We have identified neurological findings diagnostic of cervical myelopathy in a selected cohort of 270 patients previously diagnosed with fibromyalgia. An upper thoracic sensory level has been described as a false localizing sign of cervical myelopathy. Recruitment of deep tendon reflexes is an upper motor neuron sign of pyramidal tract dysfunction. Inversion of the radial periosteal reflex is felt to be virtually diagnostic of myelopathy due to extrinsic compression of the spinal cord at the level of the fifth or sixth cervical vertebra. Neuroradiological findings were consistent with a treatable structural cause(s) for the myelopathy -i.e. spondylotic cervical stenosis and/or Chiari type 1 malformation. In 20% of our patients a radiological diagnosis of the Chiari 1 malformation could be made based on tonsillar ectopia in excess of 5 mm. Meadows et al, (J Neurosurgery 2000;96:920-926), reviewed the brain and cervical spine MRI's of 22,591 patients and could identify only 175 patients in whom tonsillar ectopia exceeded 5 mm, i.e. a prevalence of 0.77%. The CT scan of the cervical spine revealed cervical stenosis, which was accentuated by neck extension. Neck extension is known to reduce the AP spinal canal diameter. The importance of imaging the cervical spine in extension in order to increase the sensitivity of detecting canal stenosis in myelopathic patients has been described by Muhle et al, (Acta Radiologica 1999; 40:146-153), and Graham et al, (Clinical Radiology 2001; 50:35-39). The AP mid-sagittal diameter at the C5/6 intervertebral disc space measured 10mm or less in 46% of patients with the neck placed in extension. A mid-sagittal diameter of 10mm is acknowledged as stenotic and consistent with symptomatic spinal cord compression, i.e. cervical myelopathy.
Spondylotic cervical myelopathy and the Chiari 1 malformation are treatable conditions. Therefore, we recommend that a detailed neurological examination should be incorporated into the evaluation of all patients with fibromyalgia. Evidence of cervical myelopathy would warrant neuroradiological examination of the brain and cervical spine and appropriate neurological referral.