Foix-Alajouanine syndrome: an uncommon cause of myelopathy from an anatomic variant circulation.

Abstract: Foix-Alajouanine syndrome is a rare cause of myelopathy caused by dural arteriovenous malformation of the spinal cord, mostly lower thoracic and lumbar. Patients are usually over 50 years of age and can present with acute lower extremity dysesthesias or intermittent sciatica. Progression to paraplegia may be slow. Spinal angiography is needed for definitive diagnosis, based on the clues provided by the symptoms. If diagnosed early, vascular embolization or neurosurgical excision may be curative.

Key Words: arteriovenous malformation, Foix-Alajouanine syndrome, myelopathy

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Foix-Alajouanine syndrome was first described in two young men (ages 31 and 37 years) in 1926. Until the middle of the 20th century, this pathologic entity was only an autopsy phenomenon. The underlying pathology was believed to be a dural arteriovenous (AV) fistula, usually in the thoracic cord. This remained the case for many decades, until the advent of high-resolution magnetic resonance imaging (MRI) and associated modern spinal angiography (Fig. 1). Even today, the true incidence of Foix-Alajouanine syndrome (FAS) is unknown and often underappreciated. (1-5)

Case Report

An 82-year-old white male was referred by his wife for progressive lower extremity weakness, worsening with exercise or standing. He reported no pain, fever, or trauma. The medical history included hypertension, paroxysmal atrial fibrillation, benign prostatic hyperplasia, and coronary artery disease. Medication included Coumadin, tamsulosin, metoprolol, and topiramate for bipolar disorder. Review of systems was significant only for shortness of breath, and recurrent chest pain was relieved with nitroglycerin. He was a retired administrator currently living in New Jersey, who did not smoke, drink, or use drugs. Examination was remarkable only for some distal sensory loss in the stocking pattern.

A preliminary thoracolumbar MRI did not show any evidence of myelopathy or vascular malformation (Fig. 2). A follow-up thoracic spine MRA showed an extensive array of blood vessels along the superior and posterior surface of the spinal cord, extending from cervical to thoracic region with associated abnormal signal intensity in the spinal cord compatible with a dural vascular fistula. Interestingly, the AV malformation was being fed by a communicating vessel from the posterior internal communicating artery (Fig. 3). This spinal AV malformation was suspected to be causing transient ischemia of his spinal cord, resulting in lower extremity weakness. The patient declined any therapeutic surgical or neuroradiology intervention on learning of the possible side effects. He was eventually referred for physical rehabilitation.

Discussion

Foix-Alajouanine syndrome is a subacute disorder that gradually evolves over 1 to 5 years. The majority of affected patients are males older than 50 years of age. About half of the patients have an acute onset of pain and dysesthesia or may complain of intermittent sciatica. Patients may have a full-blown myelopathic picture or may have transient weakness and sensory disturbances followed by progressive radiculospinal symptoms. There may also be bowel or bladder incontinence and impotence.

Pathophysiology

Symptoms are thought to be produced when there is vascular compromise and infarction of spinal cord tissue. Factors important for the pathogenesis of the radiculomyelopathy seen with the AV malformations include (1) disturbances of venous drainage caused by reduced flow in the discharging venous channels or blockage of outflow in the greatly distended convolutions and obstructed radicular arteries; (2) "steal phenomenon" resulting from the fact that the venous sink of the AV malformation acts as a shunt to siphon off blood supply from the spinal cord; (3) damage to the cord and roots caused by pressure effects of the angioma; (4) thrombosis of the abnormal vessels in the malformation. However, thrombosis is rarely demonstrated at autopsy or by angiography. All or some of these factors are responsible.

[FIGURE 1 OMITTED]

Foix-Alajouanine syndrome usually occurs in the thoracic spinal cord. Because this spinal area has the most tenuous arterial blood supply, it is most prone to injury when its vascular nourishment becomes impaired. Also, these blood vessels are so fragile that they are likely to continually bleed on an intermittent basis. Repeat exposure to foreign body substance in the subarachnoid space in the form of remittent leakage of blood from the AV malformation can initiate autoimmune amnestic reactions, which may potentiate and magnify the ongoing inflammatory process. In the case of FAS, repeated insult secondary to reoccurring subarachnoid hemorrhage typically produces severe local arachnoid fibrosis, associated thrombosis of local blood vessels and progressive destruction of the spinal cord. Normal arterial supply, venous return, and the nutrient role of cerebrospinal fluid is slowly impaired. As degeneration progresses in the spinal cord, the neural tissue may liquefy, producing a cavity. Findings include necrosis of the affected cord regions. Gray matter structures are more severely involved. Masses of enlarged, tortuous, and thick-walled subarachnoid veins are observed primarily overlying the posterior surface of the cord. The enlarged, abnormal veins are associated with a dural AV shunt, which is associated with reflux of arterial blood into the venous drainage of the cord. This results in increased venous pressure in the affected regions of the spinal cord, possibly leading to ischemic injury.

[FIGURE 2 OMITTED]

[FIGURE 3 OMITTED]

On macroscopic examination, coiled and convoluted vessels cover the spinal cord, more on the dorsal than on the ventral surface. The cord tends to be shrunken, cystic in parts, and discolored. On microscopic examination, in addition to considerable thickening and redundancy of vessels in the subarachnoid space and along the intradural parts of the spinal roots, there is also extensive demyelination and necrosis of the cord.

Because of the factors noted above, the presentation and the nature of FAS may, not unexpectedly, vary in individual cases. This is due, in large part, to each individual's unique immunologic response to the progression of acute and chronic inflammation.

Diagnosis requires a high index of suspicion because the changes are slow, so the patient may not have any neurologic symptoms until some event produces a situation. Motor neuron disease, disk disease, spinal cord tumor, and multiple sclerosis are differential considerations. Also, routine radiographs and nonenhanced MRI/computed tomography scans are highly nonspecific. Features seen on investigative modalities such as MRI of the spinal cord may show areas of high velocity signal loss within the enlarged vessels. Myelography may show filling defects caused by enlarged vessels. Cord atrophy may be present. Spinal angiography is required to define the type of the lesion and to decide about the appropriate therapy. Neurosurgical excision or vascular embolization at the early stage of the disease may be curable or, at least, halt the progression to paraplegia.

Conclusion

Foix-Alajouanine syndrome is an unusual cause of paraplegia in middle-aged patients. It can start out as transient weakness and sensory symptoms, intermittent radiculospinal symptoms, acute dysesthesias, or spastic paraparesis. An early diagnosis is essential, as untreated patients have a poor prognosis. Spinal angiography is required to define the type of the lesion, and vascular embolization at the early stage of the disease may be curable.

Be the change you wish to see in the world.
--Gandhi

Accepted October 19, 2004.

References

1. Anne G. Osborn (ed). Diagnostic Neuroradiology. St Louis: Mosby, 1994.

2. Renowden SA, Molyneux AJ. Case report: Spontaneous thrombosis of a spinal dural AVM (Foix-Alajouanine syndrome)-magnetic resonance appearance. Clin Radiol 1993;47:134-136.

3. Criscuolo GG, Oldfield EH, Doppman JL. Reversible acute and subacute myelopathy in patients with dural arteriovenous fistulas: Foix-Alajouanine syndrome reconsidered. J Neurosurg 1989;70:354-359.

4. Jellinger K. Vascular malformations of the central nervous system: a morphological overview (review). Neurosurg Rev 1986;9:177-216.

5. Koeppen AH, Barron KD, Cox JF. Syndrome. Acta Neuropathol 1974;29:187-197.

RELATED ARTICLE: Key Points

* Foix-Alajouanine syndrome is a rare cause of myelopathy caused by dural arteriovenous malformation of the spinal cord, mostly lower and lumbar.

* Progression to full-blown myelopathy or paraplegia is slow, and patients may first present with acute lower extremity dysesthesias and intermittent sciatica.

* Repetitive subarachnoid hemorrhages typically produce severe local arachnoid fibrosis, associated thrombosis of local blood vessels, and progressive destruction of the spinal cord.

* Routine imaging and nonenhanced magnetic resonance imaging/computed tomography scans may yield nonspecific findings.

* Angiography is required to define the type of the lesion, and vascular embolization in the early stages of the disease may be curative.

Rajnish Mishra, MD, and Roop Kaw, MD

From the Department of Internal Medicine and Section of Hospital and Peri-operative Medicine, Department of General Internal Medicine, Cleveland Clinic Foundation, Cleveland, OH.

Reprint requests to Dr. Rajnish Mishra, Department of Internal Medicine/NA25, Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195. Email: [e-mail]