Life With Low Serotonin, Revisited

Last year I covered the case of a young man born with a genetic disorder which caused him to suffer low levels of the monoamine neurotransmitters - serotonin, dopamine, and noradrenaline.

These are the chemicals that are widely thought to be deficient in depression, and they're the target of antidepressant drugs (especially serotonin).

If low monoamines cause depression, you'd expect someone with low monoamines to be depressed, at least on the simplest view. But the case from last year had no reported mood problems, although he did show appetite, sleep and concentration problems that were cured by serotonin replacement therapy.

Now a new case report has just appeared that tells a different story. Gabriella Horvath and colleagues from British Columbia describe two sisters. Both had a normal birth and childhood, but at the ages of 11 and 15 respectively, began to suffer severe migraines and other symptoms. Sister 1:

started having hemiplegic migraine at age 11 years, initially occurring every 3–8 weeks, lasting 4–48 hours, presenting with right or left-sided numbness and paralysis, no visual disturbances, but slurred speech, associated with vomiting, headache, and confusion, followed by weakness lasting up to 7 days, and then complete recovery. The frequency of her migraine increased slowly with age up to twice a month...

Between 12 and 20 years she had developed progressive spastic paraparesis; sensory loss in stocking distribution... urinary and bowel incontinence; bladder instability... irritable bowel syndrome; sleep problems; depressed mood; and anxiety. She needed to use a wheelchair for most of the time by the age of 17.

Sister 2 had a rather different course:

The older sister originally presented at the age of 15 years with a history of hemiplegic migraine and seizures and myoclonic jerks. EEG showed generalized spike-and-wave activity, and polyspikes with photoconvulsive [light-induced seizures] response, in keeping with juvenile myoclonic epilepsy. Her seizures were brief and infrequent and not associated with the migraine episodes...

She subsequently developed progressive weakness, frequent falls, depression, and mild bladder instability...

Various blood and genetic tests failed to get to the bottom of it. MRI scans showed abnormalities in the spinal cord and parts of the brainstem in both cases, but why?

Spinal tap studies in Sister 1 revealed very low levels of 5HIAA, which is a by-product of brain serotonin (5HT). This suggested low 5HT levels. So doctors started her on 5HTP to try to boost it.

They report that 5HTP treatment caused "improvement" in all symptoms, including the migraines, slurred speech, depression, and movement, but not immediately. She gradually went from being in a wheelchair to being able to walk around the house on crutches, although she used a wheelchair outside. However, after 3 years of treatment, at age 20, she suddenly fell into a coma lasting 2 months. She is now recovering.

Sister 2 also had low 5HIAA, and was given 5HTP. She also reported symptomatic improvement.

Blood tests reported very low platelet serotonin levels. 5HTP treatment increased this but they were still below normal. Platelet 5HT reuptake rate was also low, suggesting a problem with the 5HT reuptake transporter protein 5HTT.

But the 5HTT gene (famously known as "The Happiness Gene" although that's questionable) seemed entirely normal in these patients. The authors say however that the symptoms are, in some ways, reminiscent of mice who lack the 5HT reuptake protein (5HTT knockout mice), who also show low serotonin. Also, if it were genetic, that wouldn't explain why there were no problems at all during childhood.

So this case is a mystery. The low serotonin has no known cause, and it might just be a side effect of a deeper underlying problem, but serotonin has long been linked to migraines so it might account for some of the symptoms. The fact that 5HTP helped supports this, though it wasn't a controlled trial so we can't know for sure.

As for the depression and anxiety, improved by 5HTP, this could have been a result of low serotonin, but it could also have been a psychological reaction to the severe medical problems. It's impossible to know.

Horvath GA, Selby K, Poskitt K, Hyland K, Waters PJ, Coulter-Mackie M, & Stockler-Ipsiroglu SG (2011). Hemiplegic migraine, seizures, progressive spastic paraparesis, mood disorder, and coma in siblings with low systemic serotonin. Cephalalgia : an international journal of headache PMID: 22013141