intracranial hypotension
Reduction of cerebrospinal fluid pressure characterized clinically by headache which is maximal in an upright posture and occasionally by an abducens nerve palsy (see abducens nerve diseases), neck stiffness, hearing loss (see deafness); nausea; and other symptoms. This condition may be spontaneous or secondary to spinal puncture; neurosurgical procedures; dehydration; uremia; trauma (see also craniocerebral trauma); and other processes. Chronic hypotension may be associated with subdural hematomas (see hematoma, subdural) or hygromas. (From Semin Neurol 1996 Mar;16(1):5-10; Adams et al., Principles of Neurology, 6th ed, pp637-8)