Understanding Neurology

212CASE 3 (continued)Examination revealed normal cranial nerveand upper limb function. Tone was reduced inthe legs, with weakness of hip flexion to grade3, and grade 4 weakness elsewhere. The rightknee jerk and both ankle jerks were lost andboth plantars were upgoing. Sensory testingshowed subjective distal sensory change; therewas a loss of vibration to both knees and lostpinprick to mid shins.Abrupt onset of neuropathy is rather rare.The mixture of LMN and UMN signs limits thediagnosis to a short list of possibilities. Giventhese signs, imaging of the spine is essential.Nerve conduction studies appeared toconfirm the presence of a peripheral neuropathy,but other tests did not reveal any systemic ornutritional cause of such a neuropathy. MRI andCT scanning showed some serpiginous flowvoids over the lower thoracic cord and caudaequina (157–159).Such changes were consistent with thepresence of a dural arteriovenous fistula. Glueembolism was attempted with someradiographic success, but it had no effect on hisclinical symptoms. Further scans showed arecurrence. Further surgical ligation wasundertaken with good effect.157157 Sagittalmagneticresonanceimage,showingdural fistula(arrowheads).158 158 Magneticresonance angiogramof spinal vasculature,hunting for the sourceof dural fistula.159159 Computedtomographyangiogramillustrating thelength of duralfistula.