Secondary Schizophrenia
Essential Concepts
Before diagnosing primary schizophrenia, you must rule out secondary schizophrenia (i.e., schizophrenic symptoms are secondary to a nonpsychiatric medical disorder, either from a systemic disorder that affects the brain or from demonstrable neuropathology in the brain).
A significant minority of patients with first-episode schizophrenia, around 5%, will have an identifiable, medical etiology of their psychosis.
A wide variety of medical/neurologic disorders and some toxins are associated with psychosis.
Their diagnoses without ancillary signs and symptoms require a combination of screening, a high index of suspicion, and clinical follow-up.
Even if psychosis is the result of identifiable pathology, treatment with an antipsychotic in addition to treating the underlying disorder is often necessary.
“From error to error one discovers the entire truth.”
—Sigmund Freud, 1856-1939
Many medical disorders can potentially mimic schizophrenia. For those schizophrenia like psychoses that are the result of medical illness, I follow the suggestion of Spitzer et al. (1992) to abandon the old term, “organic mental disorder,” and use “secondary schizophrenia” instead. The distinction between primary and secondary disorders is familiar to most physicians, and it does not imply that schizophrenia is not brain based (a wrong conclusion fostered by calling it a “functional” disorder). This leaves four possibilities when faced with schizophrenic symptoms: primary schizophrenia; secondary schizophrenia (i.e., symptoms are secondary to a nonpsychiatric medical disorder, either a systemic disorder
that affects the brain or demonstrable neuropathology in the brain); substance-induced psychosis (see previous chapter); and psychiatric disorders with psychotic symptoms (see following chapter). For brevity’s sake, I still occasionally use the adjective “organic” to indicate nonpsychiatric causes.
that affects the brain or demonstrable neuropathology in the brain); substance-induced psychosis (see previous chapter); and psychiatric disorders with psychotic symptoms (see following chapter). For brevity’s sake, I still occasionally use the adjective “organic” to indicate nonpsychiatric causes.
CLINICAL VIGNETTE
A young man developed a textbook case of paranoid psychosis. During the routine workup for first-episode psychosis, a pituitary tumor was detected by magnetic resonance imaging (MRI) and partially resected. The patient now receives maintenance treatment for schizophrenia, as well as a dopamine agonist to reduce prolactin levels.
This case exemplifies the occasional scenario of an incidental discovery of a medical condition during the workup for first-episode psychosis. You will need to judge if the discovered medical condition is etiologically related to the psychosis, etiologically unrelated yet important for management, or etiologically unrelated and not important for management. In this case, the finding is etiologically unrelated to schizophrenia but complicates the management of schizophrenia (treatment with a dopamine agonist).
Johnstone et al. (1987) found organic disease (judged to be etiologically relevant for the psychiatric presentation) in 15 out of 268 (less than 6%) patients with first-episode schizophrenia. Specific conditions identified were syphilis, sarcoidosis, alcohol excess, drug abuse, lung cancer, autoimmune multisystem disease, cerebral cysticercosis, thyroid disease, and previous head injury.
TIPA multiaxial approach (i.e., simply listing schizophrenia and medical conditions without making assumptions about their relationship) is often most appropriate unless the psychosis is clearly the result of the medical disorder. If you think that controlling the medical disorder will eventually resolve the psychosis, you are probably dealing with a secondary psychosis.
DIAGNOSIS
There is no generally agreed-upon workup that every patient with psychosis must have. Follow these principles to exclude secondary schizophrenia:
Order a screening test battery to exclude common and a few selected yet very treatable disorders (Table 5.1).
An MRI will provide reassurance that a silent brain tumor (e.g., frontal lobe meningioma) is not missed, although the clinical yield of ordering an MRI will be low (Lubman et al., 2002). Expect to detect the mostly innocuous, incidental MRI abnormalities seen in 20% of the normal population (Katzman et al., 1999).
Electroencephalograms (EEGs) can be difficult to interpret since almost half of patients with first-episode schizophrenia will have EEG abnormalities of unclear significance (Manchanda et al., 2005). Moreover, a normal EEG does not exclude medial brain abnormalities and interictal psychosis (schizophrenia like psychosis of epilepsy; see below under Neurologic Conditions).
More tests are not necessarily better: Indiscriminate screening for rare disorders is inadvisable because of false-positive and false-negative test results. Order specific tests to rule in or out a disorder you suspect clinically.
Order the correct tests; for example, to exclude neurosyphilis, your patient needs to have the highly sensitive serum fluorescent treponemal antibody absorption test (FTA-Abs) and a lumbar puncture (LP), not the commonly ordered rapid plasma reagin (RPR).
In poorly responsive psychosis, expand your search to exclude a paraneoplastic syndrome, epilepsy, and sarcoidosis.
Expand your search for medical etiologies in atypical presentations (atypical with regard to age or symptoms).
TABLE 5.1. Initial Workup for First-Episode Schizophreniaa | |||||
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