Chiari Malformation and Fibromyalgia

August 9, 2010

The Chiari malformation is a relatively common occurrence. It is not necessarily a disease, nor is it truly a malformation. It perhaps should be considered, in the adult form (Chiari I malformation), to be a variant of normal. Its diagnosis is established by observing the cerebellar tonsils to be below the foramen magnum on MRI studies. Depending on the examiner's definition of the Chiari I malformation (as assessed by the amount of descent below the foramen magnum in mm), the incidence of the diagnosis may vary considerably. The extent of descent of cerebellar tonsils, however, does not necessarily correlate with symptoms, physical findings, or neurological findings. The co-existence of a Chiari I malformation with syringomyelia indicates that the Chiari I malformation has physiological significance. However, this does not necessarily imply that surgery is indicated.

Symptoms of the Chiari I malformation vary significantly from patient to patient. The symptom complex in some patients may be difficult to differentiate from the symptoms of syringomyelia, if present. The determination that a Chiari malformation is causing the symptom complex is often complicated by the overlap of symptoms that are similar to some rheumatologic disorders; hence, the alleged association between the Chiari I malformation and the diagnosis of fibromyalgia (FMS) and chronic fatigue (CFS) syndrome. This association has perhaps been taken to an extreme by some; i.e., those that consider the co-existence of FMS and CFS symptoms and the Chiari I malformation as an indication for Chiari malformation surgery. Regardless of the presence or absence of an association, it is evident that the complex nature of the diagnosis and treatment of the Chiari I malformation and syringomyelia deserves a comprehensive and methodological approach.

Chronic, widespread (multifocal) pain, fatigue, non-restorative sleep, and mood disorders are the cardinal features of FMS and CFS (1). Approximately 80% of FMS patients also have chronic fatigue, suggesting the same or similar underlying pathophysiological mechanism(s) (2 ). Headache, paresthesias, impaired cognition, alternating diarrhea and constipation, urinary frequency, orthostasis, arthralgias, tender carotid arteries also occur in about 30-50% of patients. FMS is common, occurring in 3.4% to 4.9% of women, and 0.5% to 1.6% of men (3). The prevalence is higher in patients who have any chronic condition, presumably due to changes in neuroendocrine hormones. This can be secondary to the stress associated with a prolonged illness. For example, the prevalence of "secondary" FMS is higher in patients with chronic autoimmune disorders such as systemic lupus erythematosus (SLE) or rheumatoid arthritis (RA). Undoubtedly these factors contribute to the complexity of assessing patients with a Chiari malformation, some of whom may develop "secondary" forms of FMS. A small number of patients with FMS may also have anatomic abnormalities consistent with a Chiari malformation. Furthermore, some patients with Chiari malformation and/or syringomyelia experience symptoms such as weakness, and sensory abnormalities, much like FMS patients. This underscores the immense complexity of assessing and treating these patients.

A review of selected series of classic symptomatic Chiari patients (Table-1) (4,7-11) demonstrates key features of the syndrome that occur in descending order of frequency to be:

1. weakness
2. paresthesias of the upper extremities
3. gait disturbances
4. cranial nerve involvement
5. cervical pain with headaches.

Corresponding findings at physical examination demonstrate cranial nerve palsy, upper extremity weakness and muscle atrophy with sensory abnormalities, hyporeflexia in the upper extremities and hyperreflexia in the lower extremities, Babinski and Hoffman signs, and muscle fasciculation. Although headaches are common in patients with FMS, the pain is usually diffuse, fatigue nearly universal, and the only reproducible finding is tenderness on palpation. Reflexes are exaggerated in all four extremities. In fact, the signs and symptoms of FMS and clinically significant Chiari malformations are largely mutually exclusive. Some patients, however, may have both entities. Certainly, patients with a chronic progressive neurologic condition that goes undiagnosed for years will experience significant stress. This is a key etiologic factor associated with FMS. In these select cases, surgery may improve the symptoms of the anatomic syndrome, thereby alleviating the stress associated with them (including the symptoms of FMS and chronic fatigue). Some have emphasized that gainful improvement of FMS may take many months, keeping with the hypothesis of secondary benefit. It is possible, as well, that a small number of patients have both conditions by chance alone.

Table -1. Symptoms of Chiari Malformation

a. Chiari I Malformation
b. Chiari II Malformation
c. Cervical
d. Sensory
e. Central
f. Regional

The Symptomatic Chiari neurologic Syndrome appears to be rare: only 147 patients were seen over a 6 year period at a tertiary care center specializing in cervical-cranial malformations (4). Since chronic and regional pain syndromes are very common in the general population, with prevalence rates between 10% and 20 %, one must conclude that only a very small subset of patients with FMS will also have the symptomatic Chiari malformation (or this neurologic entity is grossly underreported in the general population). A pilot study of the prevalence of MRI findings demonstrated 8 of 26 patients with FMS (31%) had some degree of tonsillar herniation compared to 11 of 15 healthy controls (73%) (5). This report suggests a much higher prevalence of this asymptomatic anatomic finding in the general population. Moreover, FMS patients did not have a higher prevalence of this radiographic finding, suggesting that essentially no relationship existed between symptoms of chronic pain and fatigue and this malformation. Claims of curative surgery for FMS/CFS where a Chiari malformation was serendipitously discovered, have led to media frenzy, and a flurry of neurosurgical procedures (6). However, this belies important differences between these two conditions. The weakness in FMS is subjective, while it is objective in clinically significant Chiari malformations. Furthermore, fatigue, widespread pain, and disturbed sleep are not features of abnormal hindbrain anatomy (e.g., the Chiari malformation).