Table 19-1 lists some of the many causes of the common type of global confusional state. The most frequent in general practice are drug intoxications and endogenous metabolic encephalopathies, mainly electrolyte and water imbalance (hypoand hypernatremia, hyperosmolarity), hypercalcemia, disorders of acid–base balance, renal and hepatic failure, hyperand hypoglycemia, febrile and septic states (“septic encephalopathy” discussed further on), and chronic cardiac and pulmonary insufficiency.
Diffuse or multifocal disease of the cerebral hemispheres is another class of transient or persisting confusional states. Concussion and seizures, especially petit mal or temporal lobe status epilepticus or the postictal state, and certain focal (e.g., right parietal and temporal) cerebral lesions may also be followed by a period of confusion. Focal lesions, most often infarctions but also hemorrhages, of the right cerebral hemisphere may evoke an acute confusional state. Such syndromes have been described with strokes mainly in the territory of the right middle cerebral artery (Mesulam et al; Caplan et al; Mori and Yamadori); usually the infarcts have involved the posterior parietal lobe or inferior frontostriatal regions, but they have also occurred with strokes in the territory of one posterior cerebral artery. A variety of more generalized or multifocal cerebral diseases may be associated with transient or persistent confusional states. Among these are meningitis, encephalitis, thrombotic thrombocytopenic purpura (TTP), disseminated intravascular coagulation, tumors, subdural hematoma, and cranial trauma.
A more restricted group of focal cerebral diseases, including drug and alcohol withdrawal and systemic infections cause delirium, as discussed below.
Pathophysiology of Confusional States
All that has been said on this subject in Chap. 16 regarding coma is applicable to at least one subgroup of the confusional states. In most cases, no consistent pathologic change is found because the abnormalities are metabolic and subcellular. As discussed in Chap. 2, the electroencephalogram (EEG) is almost invariably abnormal in even mild forms of this syndrome, in contrast to delirium tremens, where the changes may be relatively minor. Bilateral high-voltage slow waves in the range of 2 to 4 per second (delta) or 5 to 7 per second (theta) are the usual findings with confusion. These changes surely reflect one aspect of the central problem—the diffuse impairment of the cerebral mechanisms governing alertness and attention and the property of coherence imparted by these functions. If only theoretically, mental incoherence and the disorganized thinking and behavior of the confusional states reflect the loss of integrated activity of all of the associative regions of the cortex as mentioned earlier in the chapter.
This is best depicted in the patient undergoing withdrawal from alcohol after a sustained period of intoxication, that is, delirium tremens. The symptoms usually develop over a period of 2 or 3 days. The first indications are difficulty in concentration, restless irritability, increasing tremulousness, and insomnia. There may be momentary disorientation, an occasional inappropriate remark, or transient illusions or hallucinations.