The Pharmaceutical Journal
Vol 273 No 7318 p444
25 September 2004

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Weeding out the fiction more
Threat to breeding birds of the British coast more
A strange syndrome: from tics to Tourette’s more

Weeding out the fiction

A comment by Dean Wingerchuk of the Multiple Sclerosis Center of the Mayo Clinic, published in The Lancet for 24 July, examines some of the evidence for and against the medical use of cannabis for refractory neurological symptoms such as pain, spasticity, tremor and sleep disorders. In spite of assertions that cannabis confers benefits in such conditions, there have been social and legal obstacles to serious clinical evaluation of this substance.

One complicating issue is that cannabis contains hundreds of constituents, including more than 60 cannabinoids, of which delta-9-tetrahydrocannabinol is the primary active member. The discovery of cannabinoid receptors in the central nervous system, modulating psychoactive effects, offers some evidence for regarding endocannabinoid drugs as of possible value for symptom relief in people suffering from multiple sclerosis or epilepsy. It has been found that some 36 per cent of patients with multiple sclerosis in one group examined had tried cannabis, and 14 per cent had taken it to relieve their symptoms, with only 3 per cent developing dependence on it. Statistics from Canada, the US and the UK, despite different political and legal climates, have shown similar results.

Medical use of cannabis for multiple sclerosis has been associated with its recreational use and with tobacco smoking. Overall, its use in epilepsy has been associated with the use of other illicit substances and it is thought that people indulging in recreational drug experiences may pose a greater risk of resorting to cannabis and developing dependency. Many active users may be seeking to relieve secondary effects of their underlying disease, and any major mood disorders and neurological disability should be investigated.

There is little scientific evidence of the effectiveness of cannabis for neurological symptoms. There are no controlled data justifying its use in epilepsy, while in multiple sclerosis its effects on spasticity have been variable and tremor is not affected. Cannabis studies have included many variables, including formulations, dosage difficulties and method of delivery. Some patients insist that the drug is effective only when smoked. A strong placebo effect must be allowed for. Any future studies require rigid control and careful evaluation.

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Threat to breeding birds of the British coast

In Science for 20 August there is an account by Fiona Proffitt of a wildlife disturbance that is deeply worrying to ornithologists and their representative bodies such as the Royal Society for the Protection of Birds.

Recent observations of the cliffs of Fair Isle revealed a massive failure of kittiwakes, arctic terns, guillemots, razorbills, arctic skuas and great skuas to maintain their numbers. The usual noise of some 250,000 breeding birds was silenced. The breeding season has now drawn to a close on the North Sea coast of Britain, with many former colonies failing to rear any young. The phenomenon is said to be unprecedented in scale and range.

There are fears that rising sea temperatures and changing ocean currents may have affected the food supplies of the birds and so depressed their reproduction. Anecdotal evidence suggests that the prime problem is the present decline in the bottom-dwelling sand eels. Birds such as terns and kittiwakes have suffered most because they are surface feeders, whereas guillemots, which dive deeper in pursuing fish, have coped rather better.

According to experts, the most probably causes of the great decline in numbers of sand eels are overfishing, mainly by the Danish fishing fleet, and recent increases in sea temperature. Over the past 40 years the temperature of the North Sea has risen by about 1C. Kittiwakes in the locality have declined in numbers by about 30 per cent, an effect attributed to sand eel harvesting and warmer seas since 1988. In addition, increasing numbers of adult herring around Shetland may have depleted the sand eel population. Much remains to be investigated, but it is feared that the reduction in the bird population is serious and may prove difficult to remedy.

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A strange syndrome: from tics to Tourette’s

Georges Gilles de la Tourette was a neurologist who worked at the Salpêtriere Hospital in Paris. In 1885 he first described the syndrome now known by his name as the Gilles de la Tourette syndrome. Its diagnostic criteria include multiple motor tics and one or more associated vocal tics that persist for more than a year. These tics wax and wane over weeks or months, the older ones fading and new ones taking their place. The initial signs often appear in a child aged six or seven. In many they diminish significantly during the mid to late teens.

Tourette thought the condition was the result of hysteria, while other neuropsychiatrists of the period talked of repressed sexual conflicts or of oppressive mothers. Modern psychiatrists looked for organic brain defects.

In Science for 3 September, Steve Olson has reviewed current thinking about the syndrome. He points out that the wide variation in symptoms observed in sufferers makes it virtually impossible to determine the incidence of the condition. Many children show tics such as blinking or shrugging that would prompt the diagnosis. Classroom studies in the US in 1999 and 2000 indicated that 18 per cent of all children exhibited single or occasional tics and 6 per cent persistent ones. Only a fraction of these children would be diagnosed as suffering from Tourette syndrome by accepted criteria. It is considered that in the true condition groups of neurons in the basal ganglia of the brain fail to inhibit unwanted movements, which then appear as tics. Circuits from all parts of the cerebral cortex pass through these ganglia and may therefore cause manifestations of Tourette syndrome and related disorders. The neurotransmitter dopamine appears to be involved, since many drugs which block dopamine receptors also relieve the Tourette syndrome.

The ultimate cause of the disorder may be genetically determined. It tends to run in families, and is several times commoner in boys than in girls. But environmental factors also play a part, from pregnancy complications, stressful experiences in early life to random events during development. Suspicion now rests on an infectious agent, possibly the streptococcus responsible for rheumatic fever. Thus infection has been shown to exacerbate tics, but the association may be coincidental.

The treatment of Tourette syndrome has for four decades involved prescribing drugs that affect dopamine and related neurotransmitters in their action on basal ganglia. Behavioural therapy has shown some promise. Individuals are made aware of their tics by watching themselves in a mirror, when they are taught to replace that reaction with a competing muscular response that is less apparent. The goal of treatment is not necessarily to eliminate tics, but to enable more effective function within society.

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