Sleep disturbances are quite common in our society. The most common disturbance is insomnia. In 70-80% of cases, however, insomnia is secondary to unfavourable environmental or working conditions or the direct consequence of other organic or psychic pathologies. In other patients we see the opposite problem: an excess of tiredness or daytime ipersonnia, especially as a result of a complaint known as the "Obstructive apnea in sleep syndrome"/"Sindrome delle apnee ostruttive nel sonno", which does not allow the patient (often obese and a snorer), to sleep enough at night.

The most common type of ipersonnia amongst those that do not depend on other pathologies is narcolepsy. In those affected, an excessive daytime drownsiness accompanied by uncontrollable attacks of sleep is often combined with the outbreak of "cataplectic" attacks, characterized by a sudden loss of muscle tone. During these attacks, which are often caused by sudden excitement, the patient may fall to the ground and not move for several minutes, while remaining in a state of waking consciousness.

Recently, research carried out on a strain of dogs genetically affected by narcolepsy, which all had the typical symptoms of the disease (Fig. 1), has shown the link between this pathology and anomolies in the action of a chemical substance normally produced in the rear hypothalamus, know as ipocretina. The production of ipocretina is reduced in the majority of narcoleptic patients.

Fig. 1: a dog genetically affected by narcolepsy; the excitement sparked by the sight of food produces a cataplectic attack in the animal, and a sudden fall to the ground.
(Credit: taken from K9 Perspective on line: "Discovery of the canine narcolepsy gene") 

Fatal insomnia is a very serious pathology characterised by the gradual disappearance of sleep. In most cases it is linked to a hereditary genetic imbalance. Typically, the disappearance of normal sleep is associated with serious problems in the vegetative and endocrine functions and inevitably leads to death. In some areas of the brain, metabolic activity is reduced (areas shown by the arrows in the PET image, Fig. 2) and we can see a deposit of anomalous "prioni", protein molecules also found in other serious pathologies such as encefalopatia spongiforme bovina which characterize the syndrome commonly known as "mad cow disease".   Fig. 2: : Image obtained using a "positron emission tomograph" (PET) in a normal subject (Control) and in a patient suffering from Fatal Insomnia (FFI). The yellow-orange colour, indicating normal metabolic activity in the brain, is notably reduced in the frontal cortex and some parts of the thalamus of the affected patient. (Credit: Taken from P. Cortelli e C. Lombardi. Autonomic disfunction in sleep disorders. Medlink Neurology)

The Webweavers: Last modified Mon, 8 Feb 2006 11:11:15 GMT