Neurology, which has long been considered a branch of general medicine, acquires an identity of its own with the availability of investigatory means (the first electro-encephalograms) about the year 1950 and following the works of Gallais*, Collomb*, Miletto* and Guidicelli*, who direct the school of neurology at the Pharo.

In the tropics, certain particularities result due to the existence of infectious, parasitic, toxic and nutritional causes peculiar to these regions.

- The two most common causes of infection are leprosy, with its neuritis, and poliomyelitis. The second, a cosmopolitan disease, manifests itself especially by its after-effects (paralysis of the lower limbs) while epidemics may go unobserved. Mazaud* reports one of them in 1953 in Dakar. Very often, these disabled sufferers were thought to be victims of an inept injection of quinine which had injured the sciatic nerve. The discovery of the viruses responsible and an efficacious vaccine transform the incidence of this disease. During a period of ten years (1960-1970), the surgeons of the Girard and Robie Hospital in Antananarivo (P. Navaranne*) were given the responsibility, by the French Social Security, of treating the retarded after-effects of the epidemic which had affected the Reunion Islands some twenty years before. These after-effects, extensive and stable, were to be met with almost everywhere in the third world, but all the conditions necessary for their treatment were rarely available at the same time. Centres producing equipment for the disabled, as in Dakar, already put in place for invalid soldiers, are also useful for many handicapped people, in particular those suffering from leprosy.

Two great "social diseases" also come into play : tuberculosis and venereal syphilis. Tuberculosis can cause pseudotumors in the brain and, especially, lesions in the vertebral column (Pott's disease) with paralysis of the lower limbs. Both require surgical interventions (Bottreau-Roussel*, Bèzes*, Fustec*). Although not common, there are cases of neurosyphilis among the natives.

Finally, most of the great infectious diseases (typhoid, recurrent fever, rickettsial diseases in particular, etc...) can affect the brain or the meninges : their treatment and prognosis have evolved considerably in the course of the last fifty years but the beginning of this period saw the evolution of sub-acute meningitis which causes either spinal stenosis which needs liberating surgery (laminectomy) or arachnoiditis that can threaten the eyesight and can only be cured by the neurosurgical liberation of the optic chiasma (Carayon*, J.F.Blanc*). Antibiotics and corticotherapy have fortunately been effective in getting rid of these complications.

- The effects on the brain of parasitosis are mainly two types of encephalitis, one very acute and pernicious due to malaria (Gallais*, Armengaud*), the other a chronic form due to sleeping sickness (Gallais*, Miletto*, Bert*). Bert's admirable studies on its electroencephalographic evolution must be mentioned. The fame he acquires leads to his being recruited by the NASA to participate in the study of waking conditions in space. Several types of parasitosis cause abscesses and cysts that require surgery. In the brain, one has remarked cases of hydatic cysts, of cysticercosis caused by taenias, and of amoebic abscesses (J.F.Blanc*). Other diseases have more extensive effects on the brain: filariasis (Carayon*, Sankalé*), bilharziosis and, in the Far East, distomatosis caused by flukes. In Polynesia, Franco* investigated "meningitis from eosinophilic leukocyte" caused by a parasite in rats.

- As for the toxic factors, chronic alcoholism is foremost among Europeans as well as the natives : encephalopathy with delirium tremens, polyneuropathy of the lower limbs (Rainaut*). But many medicines specifically intended for tropical diseases can affect the nerves, especially emetine for amoebiasis, antimony for leishmaniasis, chloroquine for malaria (Charmot*).

- Among the illnesses due to deficiency and nutritional problems, beriberi, which proliferates in Indochina, is accompanied by a very serious polyneuropathy. It is studied by Advier* in its chronic form. Collomb*, in Dakar, describes a paralysis of the legs which he calls deficiency neuropathy (neuropathie carentielle). Finally, cases of hemiplegia can be observed in the course of Kwashiorkor.

However, the natives are not spared by any of the cosmopolitan diseases, except for multiple sclerosis held to be very rare. Epilepsy, cranial traumas (well-studied in Dakar by Carayon* and Courson* and in Antananarivo by Pigagniol* and J.F.Blanc*), cerebrovascular accidents (Collomb*, Courson* and Philippe*) and tumours have the same forms and evolutions as elsewhere.

Finally, hydrocephalus, meningoceles and other analogous ailments can only be treated according to the availability and competence of the surgeon on duty, who rarely has the necessary prosthesis at his disposal.

Page publiée le 11/01/2017.