One of the most frightening and confusing problems for the physician onboard a ship or in an isolated deployment is a patient with altered mental status. For some reason, the first concern of most physician is brain tumor or masses, a relatively rare cause of altered mental status (in the absence of trauma) in a military population. First, keep in mind the fundamentals of neurologic diagnosis. Focal disease causes focal deficits. Non-focal, that is generalized diffuse disturbance of the brain, just as anywhere in the nervous system, is due to:

History and sometimes basic laboratory tests will discriminate among these last three. The mental status examination is discussed elsewhere in this manual and will not be repeated here.

The main features that distinguish organic from psychiatric causes of mental reactions are the level of alertness and orientation. Orientation is the more useful of the two, clinically because the patient with depressed alertness is already obviously organic. When presented with a patient who is irrational or whose behavior raises the question of psychological or organic disturbances, the following considerations should come to mind: Are the patient’s sensory functions intact? Can the patient see and hear? Can the patient speak? Is the apparent strange behavior a manifestation of aphasia? Then determine the patient's ability to attend and concentrate with recall of digits or repetition of a sequence of gestures. If these are done well, the orientation to time, place, and situation are the main discriminators of organic vs. psychiatric mental disturbance. Obviously a stiff neck, asymmetry of reflexes, or a Babinski sign indicate organic disease.

Hallucinations may be signs of schizophrenia or mania, but they may be seen in organic disease as well. Visual hallucinations usually indicate organic disease, and hallucinations of small animals or bugs, especially in large numbers, indicate toxic encephalopathy. This is particularly common with drug toxicity and alcohol withdrawal.

The commonest causes of delirium (acute organic brain syndrome) are drug overdoses or chemical ingestion. Hallucinogenic drugs as well as amphetamines have to be considered, as well as narcotics and alcohol. At sea, there is plentiful access to a number of solvents. Inhalation of fluorocarbon (Freon) solvents and lubricants are occasional recreational drugs. Other ingestion may not be intentional. In a military or industrial setting, metal toxicity from lead, arsenic, and more rarely beryllium need to be considered. Many hydrocarbon solvents and fuels can be chronically and acutely absorbed through the skin and induce an organic brain syndrome. A careful history of the patient's work and recreational environments must include interviews with coworkers and bunkmates. The physician and preventive medicine techs must review the materials and chemicals used in the individual's workspace.

Acute metabolic causes of delirium include hyponatremia and hyperthermia.

Other causes of delirium without focal neurologic disease include hyperthermia, encephalitis, cerebral vasculitis, and endocrine disturbances, especially myxedema and thyrotoxicosis.

The first step in treating the patient with delirium is to identify the cause, if possible, and treat it. If the patient is agitated, phenothiazines may be the most useful agents and are less likely to be sedating than benzodiazepines. Consultation should be sought from a neurologist or psychiatrist, and if a remediable cause cannot be found, a MEDEVAC should be arranged as soon as it can be done safely.