A problem that occurs during or after a trip does not necessarily need to have a causal connection with that trip. Frequent causes of acute confusion are cerebral malaria, side effects of mefloquine, febrile delirium, acute meningitis. In acute confusion, delirium or psychosis you should:

• check the vital signs
• look for neck stiffness and consider LP
• determine whether the patient has a high temperature or not
• upon suspicion of hypoglycaemia, glucose should be administered immediately, preferably with thiamine
• perform full blood count and thick smear

A summary list of aetiologies follows below.

Delirium can occur in many febrile diseases. Confusion is prominent in typhoid fever, rickettsiosis, cerebral malaria, viral encephalitis (rabies, herpes, Japanese encephalitis, West Nile and other arboviroses), Naegleria fowleri encephalitis (amoebae), acute meningitis and cerebral abscess (tuberculous, pyogenic or amoebiasis). Endocarditis can cause septic cerebral emboli. Cerebritis and cerebellitis with ataxia can occur in Q-fever and also very rarely in Mycoplasma infections.

Syphilitic cerebral gumma, West African trypanosomiasis and cerebral toxoplasmosis cause a subacute to chronic condition. Differentiation from dementia is important. Melarsoprol used in the treatment of African trypanosomiasis can cause an acute reactive encephalitis. Chronic or subacute meningitis due to tuberculosis or cryptococcosis, can occur in AIDS.

Worm infestations of the central nervous system tend to provoke severe symptoms. Infection with Angiostrongylus cantonensis, cysticerci, Echinococcus, Gnatostoma sp, Toxocara sp and ectopic migrations of schistosomes or Paragonimus sp usually cause acute symptoms. The cerebrospinal fluid can contain eosinophils. Schistosoma japonicum especially affects the brain during ectopic migration. S. haematobium and S. mansoni more often cause lesions in the spinal cord, though these findings are not proven.

Mefloquine -in some cases- causes severe side effects, such as confusion, dizziness or acute psychosis.

Individuals who take monoaminoxidase (MAO) inhibitors and experiment with plants that contain substances that can cause interactions with these (e.g. harmin contained in ayahuasca, Banisteropsis caapi) can develop acute confusion and delirium.

Cerebral oedema. In high mountainous areas one should watch out for acute cerebral oedema due to altitude sickness in cases of acute confusion, Cheyne-Stokes respiration, ataxia, disorientation or other neurological problems. Fast administration of oxygen and dexamethasone and immediate evacuation to an area at lower altitude with medical infrastructure is imperative. Acetazolamide (Diamox®) can be used prophylactically with limited efficacy.

It should of course be borne in mind that an already existing cardiovascular disease can worsen the relative hypoxia at high altitude.

A poorly burning stove in an unventilated environment can cause carbon monoxide poisoning (CO-intoxication).

Mefloquine taken for malaria prevention in low-lying areas and continued to be taken in the mountains can result in confusion. The same warning applies for alcohol.

Caisson disease. In acute confusion, stupor, neurological problems or shock occurring after diving, one should consider decompression problems or caisson disease resulting from too rapid ascent to the surface (often occurs in panic situations).

Rupture of the lung with pneumothorax can occur due to rapid ascent to the surface without adequate expiration. For example, the pressure amounts to 3 atmospheres at a depth of 20 metres while on the water surface it is only one atmosphere so that the lungs’ volume would have to increase threefold. The air in the lungs expands as the pressure falls.

Envenomation by certain marine animals can have hyperacute and very serious consequences. The sea wasp [Chironex fleckeri] is a small, translucent, but extremely venomous jellyfish that is found in Australasian seawater. Coneshells [Conus sp] can likewise deliver a highly venomous sting (nerve toxin). The bite of the so called "blue ringed octopus" [Hapalochlaena lunulata and H. maculosa], a name given to two related species of small cephalopods (15 cm) found in the seas between Northern Australia to Japan, is likewise notorious. Acute confusion and stupor are among the clinical symptoms. Irukandji syndrome occurs in North Australia following stings by Carukia barnesi, a small box jellyfish.

• Severe ketoacidosis, usually in diabetes

• Wernicke-Korsakoff’s disease (frequent with alcohol abuse). Acute deterioration can be triggered by intravenous glucose administration. Paresis of the eye muscles, together with ataxia in a patient with confusion and apathy, with recovery after injection of thiamine (vitamin B1), is diagnostic. (cf. beriberi)

• Severe hyponatraemia, such as is occasionally seen in SIADH (Syndrome of Inappropriate Secretion of Antidiuretic Hormone) and in Addisonian crisis (adrenal failure, e.g. after a bite from a Russell’s viper).

• Heat stroke and dehydration. Definitely increased risk in the tropics. Heat illness may be viewed as a continuum of illnesses relating to the body’s inability to cope with heat. It includes minor illnesses, such as heat edema, heat rash (ie, prickly heat), heat cramps, and tetany, as well as heat syncope and heat exhaustion. Heatstroke is the most severe form of the heat-related illnesses and is defined as a body temperature higher than 41°C associated with neurologic dysfunction. Two forms of heatstroke exist. Exertional heatstroke generally occurs in young individuals who engage in strenuous physical activity for a prolonged period of time in a hot environment. Classic nonexertional heatstroke more commonly affects sedentary elderly individuals, persons who are chronically ill, and very young persons. Classic nonexertional heatstroke occurs during environmental heat waves and is more common in areas that have not experienced a heat wave in many years. Both types of heatstroke are associated with a high morbidity and mortality, especially when therapy is delayed. Hypoglycemia, convulsions and rhabdomyolysis can occur as complications of heatstroke.

• Severe hypothyroidism with possible myxoedemic coma. Thyroid problems can get worse after using iodine for drink water decontamination.

• Drunkenness. Beware of methanol contamination of home-brewed liquors.

• Intoxication: acute e.g. CO, cocaine (crack), chronic in e.g. mercury- or thallium intoxication (rat poison). Intoxication with thallium causes hair loss several weeks after the acute poisoning.

• Cerebrovascular accident due to thrombosis or cerebral embolism (increased risk in Chagas’ disease, endocarditis, sickle cell crisis).

• Loasis (Loa loa infection) with high microfilariaemia can cause acute neurological symptoms, often just after commencement of therapy.

• Hypertensive encephalopathy is usually clinically manifest. It is a medical emergency. Blood pressure is very high and the eye fundus is typical.

• Inflammation of the brain and/or meninges (see above). Cerebral vasculitis can occur in a systemic disease such as systemic lupus erythematosus. Immunosuppression in SLE-patients, e.g. by therapy with steroids, increases the risk of some complications, such as tuberculosis, including meningeal tuberculosis (not infrequent in India). Beware of Strongyloides hyperinfection when people use corticosteroids.

• Head injury, with concussion or subdural haematoma.