67‐YEAR‐OLD MAN WITH PROGRESSIVE PARAPARESIS

CLINICAL HISTORY AND NEUROIMAGING

A 67‐year‐old male, who had no significant past medical history, presented with a 4‐year history of progressive paraparesis, lower extremity sensory loss and dysesthesias. He was initially diagnosed and treated for peripheral neuropathy, but his symptoms progressed. Further work‐up revealed degenerative changes in his lumbar spine, and he underwent a laminectomy at L4–5 for significant stenosis. Unfortunately this surgical procedure also did not alleviate his symptoms. He eventually progressed to complete paraplegia with an associated sensory level at T11 and loss of sphincter control. Other findings on physical examination included significant muscular atrophy and spasticity, with positive clonus and Babinski sign in his lower extremities but not in his upper extremities. He otherwise had no other neurological or constitutional symptoms or signs.

Cerebrospinal fluid studies for bacterial, viral, fungal infections, sarcoidosis, demyelinating diseases and neoplastic processes were negative. T1‐weighted magnetic resonance imaging scan, with gadolinium, revealed a serpiginous, inhomogeneously enhancing, intramedullary lesion extending from the conus medullaris to the T9 level (Figure 1). Selective intercostal and lumbar artery angiogram did not reveal any spinal vascular malformations, dural arteriovenous malformation or atypical vascularity. A diagnostic thoraco–lumbar laminectomy and spinal cord biopsy were performed. The spinal cord appeared atrophic with yellowish white surface discoloration. No arteriovenous malformation could be identified along the exposed spinal cord, either superficially in the leptomeninges, in the adjacent dura or within the deeper parenchyma of the cord itself.

Figure 1.

MICROSCOPIC FINDINGS

Small biopsies revealed remote cavitation of cord parenchyma, with the old areas of infarct containing only scattered residual macrophages and innumerable thickened hyalinized small vessels (Figure 2). The surface of the spinal cord manifested severely fibrotic leptomeninges, surface vessels and small parenchymal vessels, which were highlighted by Masson trichrome stain (Figure 3). Numerous small vascular “collagen tubes” were seen within the areas of cord necrosis (Figure 4). Vessels were so thickened that they were not recognizable as arteries or veins, and were negative for amyloid on Congo red stain. Small vessels lacked the close juxtaposition of true cavernous angioma. A few non‐neoplastic mononuclear cells were seen in the area of the remote infarction and focally within leptomeningeal vessel walls (Figure 5), but no fibrinoid vascular necrosis was apparent. Dilated, telangiectatic vessels throughout the cord suggested alteration in spinal cord vascular circulation even in areas without the severely hyalinized vasculature. No neoplasm was identified.

Figure 2.

Figure 3.

Figure 4.

Figure 5.

DIAGNOSIS

Subacute necrotic myelitis/myelopathy (Foix–Alajouanine syndrome).

DISCUSSION

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 2, 3). 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 caused by previous infection, inflammation and scarring of the 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 caused by hypotension, emboli or aortic atherosclerotic disease (2). The blood vessels have the appearance of an acquired abnormality because of the “arterialization” of veins from excess vascular pressure and lack of the close juxtaposition of a true cavernous angioma. Smaller hyalinized intraparenchymal vessels have been appropriately dubbed as “collagen tubes”(5). 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 caused by altered circulation following spinal cord infection, but rather were associated with the presence of an arteriovenous fistula of the dura (1). 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 because of either spontaneous thrombosis of the fistula or inadequate angiography (4). 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.

ABSTRACT

A 67‐year‐old male presented with a 4‐year history of progressive paraparesis, lower extremity sensory loss and dysesthesias. Surgery for lumbar spinal stenosis failed to alleviate his symptoms or stop progression of the disease. He eventually developed complete paraplegia and loss of sphincter control. Magnetic resonance imaging scan revealed a serpiginous, inhomogeneously enhancing, intramedullary lesion, extending from the conus medullaris to the T9 level. Angiography failed to disclose a dural arteriovenous malformation. Small biopsies demonstrated remote cavitation of the spinal cord parenchyma, associated with innumerable, thickened, hyalinized, small vessel “collagen tubes.” Overlying leptomeninges were severely fibrotic and contained hyalinized, but not occluded, vasculature. No neoplasm was identified. Diagnosis was subacute necrotic myelopathy (Foix–Alajouanine syndrome). The age of the patient, clinical symptoms and spinal cord location in this case are classic for the syndrome. Features are thought to be caused by excessive localized venous pressure that insidiously alters spinal cord leptomeningeal and parenchymal vasculature, with steal and chronic ischemic damage. Although often associated with a dural arteriovenous malformation, up to 1/5 of cases may fail to show angiographic abnormalities.