Cognitive scores after 5-day ketamine infusions for hard-to-treat chronic migraine

The question

Do people with chronic migraine that has not responded to other treatments show changes in thinking and memory in the year after receiving a multi-day ketamine infusion in hospital?

What they did

Adults with refractory chronic migraine and severe migraine-related disability, who had already failed at least one other inpatient intravenous treatment, were recruited before a planned hospital admission. They received a continuous ketamine infusion over 5 days, up to a maximum rate of 1 mg/kg per hour. Cognitive function was measured with a telephone version of the Montreal Cognitive Assessment (a short screening test of memory and thinking) at the start and again at 1, 6 and 12 months, along with pain, migraine days and disability measures. Twenty-three patients were analyzed.

What they found

Average age was 44.8 years, 87% were women, and 82.6% had a history of depression. The average telephone cognitive score was 18.8 at baseline, 19.9 at 1 month (p < 0.001), 19.2 at 6 months (p = 0.390) and 18.3 at 12 months (p = 0.382); only the 1-month change met the 1-point threshold considered clinically meaningful. Monthly migraine days fell from 27.1 at baseline to 24.4 at 1 month (p = 0.08), 22.4 at 6 months (p = 0.05) and 22.3 at 12 months (p = 0.026). The authors note that a few individual patients had worsening cognitive scores.

The fine print

Only 23 people took part, there was no control or comparison group, and everyone knew they were receiving ketamine, so improvement or stability cannot be credited to the drug itself. The telephone cognitive test is a brief screening tool rather than a detailed assessment, and repeat testing can produce practice effects. Participants were a selected group with severe, treatment-resistant migraine and a high rate of depression, so results may not generalize. This summary is based on the abstract only.

What it means

In this small group, cognitive screening scores did not decline on average over a year after a 5-day ketamine infusion, though a few individuals did worsen and the study was too small and uncontrolled to settle the safety question.

Evidence grade: Low. Small prospective observational study with no control group or comparison treatment, so changes cannot be attributed to ketamine alone.

This summary is based on the study’s published abstract.