Infarction of the anterior spinal artery territory manifests with bilateral segmental lower motor neurone weakness and, below the level of injury, pyramidal signs and loss of pain and thermal sensation. Two patients presented with neuropathic upper limb pain and flaccid paralysis ipsilateral to a unilateral infarction, no pyramidal signs and contralateral loss of thermal and pain sensation. We consider the site of vascular pathology and the mechanism of the ipsilateral pain.Methods and Results
Two women, 22 and 24 year-old, had acute unilateral neuropathic pain and weakness of the right upper limb and contralateral thermoalgesic sensory loss. Denervation on the side of paralysis followed. CSF and SSEPs were normal. Thermal Sensory Analysis showed thermal hypoesthesia and hypoalgesia contralateral to the pain and motor deficit. Contact heat evoked potentials were absent or smaller from the arm contralateral to the paralysis. MRIs showed abnormal signal in right anterior spinal artery territory at C1–2 to C4–5, and predominantly unilateral at C3–4 to C4–5 respectively.Discussion
The territory matches the sulcal commisural artery (SCA), a branch of the anterior spinal artery (ASA).1 Double ASA and double SCA are described.2 This territory can also be affected by proximal pathology of the ASA, feeding radicular arteries3 and vertebral arteries.4 The ipsilateral pain may be attributed to ischaemia of ventral root afferent fibres; in the cat they supply cutaneous or visceral structures from the limbs or innervate the ventral root proper, or its sheath, and respond best to noxious stimuli.5,6 In humans the failure of dorsal rhizotomy to relieve neuropathic pain was attributed to ventral root unmyelinated axons,720% of ventral roots axons are unmyelinated8 and electrical stimulation of leg sensory nerves elicited small potentials in the ventral roots.9Conclusion
Unilateral anterior cervical cord infarction can present with segmental acute ipsilateral neuropathic pain and lower motorneuron weakness, contralateral spinothalamic loss and no pyramidal signs below the infarction level. The territory affected may be that of a sulcal commissural artery. The ipsilateral pain suggests that a subset of human afferent ventral root sensory fibres plays a functional role in pain.Funding
Fondecyt (Chile) Grant N°1120339.