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A sudden spinal syndrome—often pain followed rapidly by weakness, a sensory level and sphincter disturbance—would raise suspicion of haematomyelia. Symptoms can localise injury to the spinal cord, but cannot prove that the material within it is blood.

The classical presentation is abrupt severe spinal or radicular pain followed by rapid loss of motor power below the affected level. A thoracic lesion can produce paraplegia; a cervical lesion can affect all four limbs, and a high cervical lesion can impair breathing. Bladder retention or loss of control and bowel disturbance support interruption of descending spinal pathways. Sensory examination may show a sensory level below which sensation is altered; the distribution need not be perfectly symmetrical.

A centrally placed haemorrhage can especially injure crossing spinothalamic pathways and the anterior horns. There may therefore be disproportionate loss of pain and temperature with relative preservation of some other modalities, together with segmental weakness, reduced reflexes or later wasting at the level of the lesion. Damage to descending motor pathways produces weakness below it. Acute spinal shock can initially suppress reflexes below the lesion; later reflex behaviour depends on the pathways destroyed and should not be predicted from the first examination alone.^[ref]

The history should look for trauma, a bleeding disorder or anticoagulant exposure, a vascular malformation or an underlying spinal lesion. In a modern assessment these are possible causes, not prerequisites. A haemorrhage can also develop subacutely or recur, so the apoplectic onset is suggestive rather than universal.^[ref]

Important alternatives are spinal cord infarction, acute inflammatory myelitis, traumatic injury without intramedullary bleeding, and an epidural or other extramedullary collection compressing the spinal cord. A spinal meningeal bleed is anatomically different from haematomyelia, even if pain and weakness overlap. Preserved consciousness and absence of cranial signs may support spinal localisation, but neither is an absolute rule.

Modern magnetic resonance imaging is required to demonstrate the location and nature of the lesion; it can distinguish intramedullary blood from external compression and guide investigation of an underlying vascular or neoplastic cause.^[ref] In an 1864 answer, sudden onset and anatomical localisation justify a suspected diagnosis; they do not justify claiming certainty from symptoms alone.