Lumbar puncture (LP), a common diagnostic procedure, is usually associated with low morbidity. We describe the case of a 29-year-old woman who underwent a non-traumatic LP in the setting of normal coagulation. Cauda equina syndrome subsequently developed secondary to an extradural spinal haematoma. Avoidance, identification and management of this uncommon complication are discussed. Iatrogenic cauda equina syndrome following LP is rare, but can cause significant morbidity. Our patient's experience and our review of the literature highlight that: (i) normal coagulation and a non-traumatic LP do not exclude this diagnostic possibility; (ii) early recognition determines the management and prognosis, as 50% of patients remain paraplegic if the condition is identified more than 12 hours after symptom onset; and (iii) neurosurgical intervention can be avoided, despite bladder dysfunction, if there are early signs of recovery.