DIAGNOSIS: Subacute necrotic myelitis/myelopathy (Foix-Alajouanine syndrome)
This case fits the definition for Foix-Alajouanine syndrome, also known in the literature as "angiohypertrophic necrotizing myelitis", "angiodysgenetic myelomalacia", and "angiodysgenetic necrotizing myelopathy". The syndrome was first described in 1926 by C. Foix and T. Alajouanine in two men who had experienced several years of progressive flaccid paralysis (1,2). The patients eventually succumbed to sepsis; at autopsy there was spinal cord necrosis associated with enlarged, tortuous, hyalinized veins on the surface of the cord and numerous small fibrotic blood vessels within cord parenchyma. The original authors attributed these changes to alterations in the local venous circulation due to previous infection, inflammation, and scarring of spinal cord vasculature.
The presence of severely altered ("angiodysgenetic") blood vessels associated with cord necrosis sets this condition apart from remote traumatic injury to cord, syringomyelia, or spinal cord infarction due to hypotension, emboli, or aortic atherosclerotic disease (2). The blood vessels have the appearance of an acquired abnormality due to "arterialization" of veins from excess vascular pressure and lack the close juxtaposition of a true cavernous angioma. Smaller hyalinized intraparenchymal vessels have been appropriately dubbed "collagen tubes" (3). Most abnormal vessels appear to be very fibrotic veins or capillaries, although the vasculature may be so altered that exact identification is impossible. After the first descriptions, it was subsequently realized that most cases of Foix-Alajouanine were not due to altered circulation following spinal cord infection but rather were associated with the presence of an arteriovenous fistula of the dura (4). The most common location is in the lower thoracic or upper lumbar spine, although cervical and upper thoracic locations have been described. Angiography will usually reveal the presence of an arteriovenous dural fistula. However, about 19% of angiographic spinal cord exams fail to demonstrate this fistula even when it is present. This is believed to be due either to spontaneous thrombosis of the fistula or inadequate angiography (5). Blood supply within the spinal cord is not only provided by the intercostal and lumbar arteries, but may be from other arterial sources often overlooked during a regular angiography. Clinically, although the original two cases of Foix and Alajouanine were young men, ages 31 and 37 years, today most cases occur in male patients over 50 years of age (2). Patients present with progressive lower extremity motor and sensory changes and loss of sphincter control. About half develop lumbar pain. An average delay of 24 months exists in correct diagnosis of the condition. Most patients, including this one, are initially diagnosed as having polyneuropathy, transverse myelitis, syringomyelia, degenerative spine disease including stenosis or herniated disks, or a spinal tumor.
Contributed by Kerry Brega, Lars Widdel, B. K. Kleinschmidt-DeMasters