Abducens palsy occasionally has been observed after diagnostic lumbar puncture (DLP). 1-3 Its risk is not exactly known. We are aware of only one report, which mentions not a single case among 1,341 DLPs when using 22-gauge needles. 4 At our clinic, an average of 800 inpatients a year undergo DLP. We usually use 22gauge needles, and occasionally (in less than 5%), 20-gauge needles. Over a 14.5-year period, we saw two patients with abducens palsy-one unilateral, one bilateral-after DLP. This translates to a risk of less than 1 out of 5,800 DLPs.Patient reports. Patient 1. A 61-year-old man with type 2 diabetes noticed progressive weakness of the legs. Neurologic examination revealed proximal paraparesis, loss of deep tendon reflexes of the legs, diminished sensation to touch and pain in a stocking-like pattern, and diminished vibration sense. Nerve conduction studies documented sensorimotor demyelinating neuropathy of the legs and, less pronounced, of the arms. DLP was done with a 22-gauge needle and was not followed by postlumbar puncture headache. After 7 days, he noticed horizontal diplopia when looking to the right. There was a right-sided abducens palsy. MRI documented small bifrontal and parietal hygromas and diffuse meningeal gadolinium enhancement (figure). Abducens palsy recovered completely within 4 months.Patient 2. A 33-year-old man with type 2 diabetes noticed exercise-related pain in the calf and thigh muscles (finally attributed to a myoadenylate deaminase deficiency). Neurologic examination revealed bilateral loss of ankle jerks and diminished sensation to touch and pain in a stocking-like pattern. Nerve conduction studies documented sensory demyelinating neuropathy of the legs and, less pronounced, of the arms. After DLP with a 22-gauge needle, he developed mild postlumbar puncture headache recovering within 7 days. Two days later (9 days after DLP), he noticed horizontal diplopia when looking to the left and right. There was a bilateral abducens palsy. MRI documented diffuse meningeal gadolinium enhancement. Abducens palsies completely recovered within 7 months.Discussion. Sixth nerve palsy after DLP is attributed to continuous CSF leakage through the dural hole. 2,5 This results in intracranial hypotension with MRI-documented descent of the brain even in the supine position, causing traction of the VIth nerve and pain-sensitive structures (dura, blood vessels, nerves). 5 This also explains orthostatic headache, which is usually associated with post-DLP abducens palsies. 1,2,5 The needle size seems to be crucial for both post-DLP abducens From the Departments of Neurology (Drs. Thömke, Mika-Grü ttner, and Visbeck) and Neuroradiology (Dr. Brü hl),