The tests that should be performed on patients with mood, emotion, or thought disorders depend on the clinical situation. Patients who present for the first time are obviously to be evaluated differently from patients who were once fully evaluated but have suffered a relapse. Patients with long histories, although perhaps never fully evaluated with modern techniques, may not require testing because the natural course of alternative diagnoses may preclude their consideration (e.g., in a 65-year-old with a 40-year history of schizophrenia, a frontal lobe tumor is not the cause of the behavioral disorder).
Neuroimaging. There are some who believe that all psychotic patients should have at least one brain imaging study. A magnetic resonance imaging (MRI) study is more sensitive than a computed tomography (CT) scan primarily because it reveals white matter disease with far greater sensitivity. The usefulness of these studies is questionable in "routine" disorders of mood, emotion, and thought, but in atypical cases, those of late onset, or when focal neurological signs are present, an imaging study is imperative. In general, imaging is done to look for evidence of masses or infarcts for which CT is adequate. Lesions causing such changes are usually large or multiple, and CT is satisfactory and much less costly than MRI. In patients who have had a prior brain imaging study for a behavioral disorder, repeat studies are unlikely to shed further light on a potential organic cause.
SPECT studies have been available for several years using the hexamethylpropylenamine-oxime (HMPAO) ligand to visualize brain metabolism, yet they have little diagnostic value for individual patients. In the future, as more ligands are developed, the prospect of depicting neurotransmitter or receptor densities throughout the brain is high. PET scans provide information about metabolism (glucose utilization), neurotransmitters, or receptors. Although several abnormalities have been found in a variety of disorders of mood, emotion, and thought, none occur with sufficient specificity to be diagnostic.
Electrophysiology. Electroencephalography (EEG) is helpful in the evaluation of seizure disorders and metabolic encephalopathy and, to a lesser extent, for documentation of regional physiological malfunctions. In patients with psychosis, the EEG should be normal, whereas metabolic disorders can cause disorganization and generalized slowing. The EEG can reveal physiological abnormalities that may not be reflected on structural imaging studies. Old trauma, a postictal state, or migraine headache may be associated with behavioral abnormalities and may cause focal EEG findings when the mRi is normal. Rarely, disorders of emotion, mood, or thought with "subclinical seizures" or complex partial status epilepticus may be diagnosed only with EEG. The use of evoked responses in neuropsychiatric disorders remains a research tool except when organic explanations such as multiple sclerosis are being actively considered.
Body Fluid and Tissue Analysis. "Routine" blood tests to assess for metabolic disorders are required for all patients with behavioral abnormalities. Sodium, glucose, creatine, blood urea nitrogen, calcium, liver function tests, and thyroid hormone levels are mandatory. Depending on the situation, other blood studies such as serum ammonia, ceruloplasmin, porphobilinogen, drug levels, prolactin and other hormones, toxicology screens, vasculitic studies, and HIV and syphilis serologic tests may be appropriate. Gastric lavage is useful in patients with suspected drug ingestion and possibly when one is looking for blood as a source of hepatic encephalopathy. Genetic testing can be done when Huntington's disease is considered likely. Because of the putative biological nature of many depressions, certain research-related tests have been developed, including the dexamethasone suppression test, measurement of urinary
USEFUL STUDIES IN THE EVALUATION OF PATIENTS WITH DISORDERS OF MOOD, EM
OTION, AND THOUGHT
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