Upward spinal coning: impaction of occult spinal tumours following relief of hydrocephalus.

Neurological deterioration sometimes follows removal of cerebro-spinal fluid by lumbar puncture below a spinal block caused by a tumour. Experience has shown that similar impaction of a spinal intradural tumour may occur following the draining of hydrocephalus. We have used the term "upward spinal coning " to describe this and report four cases in which impaction of an intradural metastasis occurred when the obstructive hydrocephalus caused by the primary intracranial tumour was relieved. The possible mechanisms are discussed. Awareness of the syndrome is important for early diagnosis and treatment and motor power should be assessed regularly following the relief of hydrocephalus caused by a tumour known to seed in the spinal subarachnoid space.