148 7 Diseases of the Spinal Cord

risk. The initial presentation is often with (poly-)radicu- lar deficits due to narrowing of the intervertebral foramina; as the spinal canal itself becomes increasingly stenotic, clinically evident spinal cord compression develops. Patients typically complain at first of paresthesiae in the fingers and impairment of the sense of touch (examination reveals astereognosis). The intrinsic muscles of the hands may become atrophic. Ulti- mately—or, rarely, as the sole manifestation—involve- ment of the long white matter tracts produces spastic paraparesis, enhanced reflexes, and pyramidal tract signs. Neuroimaging is essential for the establishment of the diagnosis; MRI is best (Fig. 7.8). Neurosurgical decompression of the spinal canal, possibly with spinal stabilization (fusion) at the same procedure, generally arrests the progression of the neurological deficits.

Fig. 7.8 Myelopathy in cervical spondylosis. The T2-weighted MR image reveals narrowing of the spinal canal at C5/C6 and C6/C7 both anteriorly and posteriorly because of degenerative spondylotic changes. A signal abnormality in the spinal cord below C6/C7 indicates a lesion induced by compression.

Circulatory Disorders of the Spinal Cord

Vascular lesions of the spinal cord, as of the brain, are of two main types: hemorrhage and ischemia. The latter is due to blockage of either the arterial blood supply (e. g., because of thrombosis or embolism) or the venous outflow.

Blood Supply of the Spinal Cord

The spinal cord receives arterial blood from three vessels: the unpaired anterior spinal a., which runs down the anterior median fissure of the cord and supplies the anterior two-thirds of its cross-sectional area, and the paired posterolateral spinal aa. Each of these spinal arteries is made up of a series of individual segments that are linked with one another along the longitudinal axis and receive arterial blood from various sources (Fig. 7.9). At cervical levels, the anterior spinal a. receives blood mainly from the vertebral a. and the costocervical and thyrocervical trunks; further down the spinal cord, it is supplied by segmental arteries arising from the aorta (spinal branches and radicular arteries, each of which has an anterior and a posterior branch). In the embryo, there is a radicular artery for each spinal segment; postnatally, only six to eight such arteries are still present. The largest of these, called the great radicular a. or the artery of Adamkiewicz, usually enters the spinal canal between T10 and L2, more commonly on the left side. The anatomy of the spinal vessels is shown in Fig. 7.9 and the intramedullary blood supply of a cross-section of the cord in Fig. 7.10. Venous blood flows out of the spinal cord through radicular veins and into the vena cava.

vertebral a.

radicular a.

aorta

great radicular a. (of Adamkiewicz)

Fig. 7.9 Blood supply of the spinal cord (diagram, longitudinal view).

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			Circulatory Disorders of the Spinal Cord		149
Fig. 7.10 Blood supply of the spinal			posterior spinal aa.
cord (diagram, cross-sectional view).	corticospinal tract	3
Occlusion of the anterior spinal a. pro-
		2	1
duces infarction in the area shaded in	lateral
gray.				1 arm/hand
	spinothalamic tract
				2 trunk
				3 leg/foot
	vasocorona
			1	2 3
	sulcocommissural a.

anterior spinal a.

radicular a.

Arterial Hypoperfusion

Global (arterial) myelomalacia. Infarction of the entire cross-section of the spinal cord at a particular level may be due to the occlusion of a local spinal artery or of a radicular artery, or to extraspinal vascular pathology, such as an aortic aneurysm. The clinical presentation is usually an acute spinal cord transection syndrome (complete or partial, see p. 142), though, in some patients, symptoms develop subacutely over the course of a few days, or stepwise. Affected patients usually remain paraplegic, particularly if the ischemic lesion is very extensive.

Anterior spinal artery syndrome. Thrombotic or embolic occlusion of the anterior spinal a. damages the anterolateral aspect of the spinal cord over one or more segments. The characteristic clinical manifestations are described above on p. 143. An occlusion at a distal location along the course of the anterior spinal a., e. g., in a sulcocommissural artery (cf. Fig. 7.10), may cause a partial Brown−Séquard syndrome (Table 7.1), with preservation of the sense of touch.

Central cord infarction. Infarction of the spinal cord, whether it involves the entire cross-section of the cord or only a part of it, is usually not restricted to a single cord segment in the vertical dimension, but rather tends to involve multiple segments. As part of this process, necrosis affects the motor neurons of the anterior horn, causing flaccid paresis and areflexia at the level of the lesion, in addition to the spastic paresis below the level of the lesion due to involvement of the corticospinal tracts. In a few weeks’ time, the flaccid muscles become atrophic. The clinical picture is, therefore, that of a “peripheral” paralysis at the level of the transection and also a short distance below it.

Intermittent spinal ischemia is very rare and causes a type of spinal intermittent claudication with fluctuating spastic paraparesis.

Chronically progressive vascular myelopathy can cause slowly progressive spastic paraparesis, as well as muscle atrophy owing to involvement of the anterior horns.

Impaired Venous Drainage

Spinal cord ischemia due to impaired venous drainage is a rare cause of infarction. It is usually due to a spinal arteriovenous fistula or arteriovenous malformation.

Spinal Arteriovenous Malformations and Fistulae

Arteriovenous malformations are usually found in the thoracolumbar region, while fistulae are usually found at lower lumbar levels (Fig. 4.10, p. 51). Both types of vascular anomaly are more common in men. They tend to present between the ages of 10 and 40, often with

(bandlike) pain as the initial symptom. Neurological deficits referable to the spinal cord are often only intermittent at first and are (partially) reversible at this stage; later, they take a chronic, progressive course and become permanent. A dural arteriovenous fistula, for example, can cause chronically progressive spastic paraparesis. These vascular anomalies also occasionally present with spinal subarachnoid hemorrhage. MRI is the most important diagnostic study for the establishment of the diagnosis. Spinal angiography can provide useful additional anatomical detail.

7

Diseases of the Spinal Cord

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