Schizophrenia or Traumatic Brain Injury?

Psychosis following traumatic brain injury (TBI) is a rare, but serious condition. TBI-related psychosis differs qualitatively from primary psychotic disorders and often has a better prognosis, though the prognosis is largely dependent upon the circumstances surrounding the brain injury (Ahmed & Fujii, 1998). Much like in a primary psychotic disorder, such as schizophrenia, hippocampal degeneration has been identified as a source of dysregulation of the dopaminergic circuit.

Interestingly, individuals with mild as well as severe TBI can experience post-injury psychosis. Some predisposing factors that make post-injury psychosis more probable include adolescent cannabis use (Rabner, Gottlieb, Lazdowsky, & LeBel, 2016). While those with TBI-related psychosis tend to have some family history of psychosis, those with a primary psychotic disorder are more likely to have a stronger family prevalence of schizophrenia (i.e. immediate family) or other psychotic illness (Fujii, 2002).

Clinically, TBI-related psychosis can present in two forms: (1) delusional type or (2) schizophrenia-like psychosis. Delusional disorders resulting from TBI most often include persecutory or paranoid delusions in the absence of hallucinations or other positive symptoms of psychosis (Fujii, 2002). There is some evidence to suggest that delusions of a grandiose or religious nature may more likely indicate a primary psychotic disorder. Moreover, TBI-related psychosis may present with more “neurological” based delusions such as Capgras delusion, wherein the individual believes someone has been replaced by an imposter. In the schizophrenia-like psychosis type, individuals with TBI will exhibit auditory, and occasionally visual, hallucinations in addition to paranoid and delusional beliefs (Batty, Rossell, Francis, & Ponsford, 2013).

Perhaps most striking, patients with psychosis secondary to TBI are much less likely to exhibit negative symptoms than those with a primary psychotic disorder. As such, the presence or absence of negative symptoms may be a good diagnostic indicator. Imaging techniques may also be useful to foster diagnostic clarity. Namely, MRI in psychosis due to TBI is most likely to reveal focal damages to either frontal or temporal regions, whereas a primary psychosis, such as schizophrenia, is associated with enlarged ventricles on imaging (Fujii & Ahmed, 2001).

Issues that complicate differential diagnosis

The differential diagnosis for TBI-related psychosis versus schizophrenia can be quite difficult for a variety of reasons. For those with a TBI, psychotic symptoms may not manifest for 1 to 20 years after the injury has occurred, with the most typical latency onset being 1 to 4 years post-injury. Of note, most individuals who go on to develop psychosis after a TBI are likely to present with symptoms within the first year. Moreover, there is some evidence to suggest that latency duration has clinical significance. Specifically, those with a shorter latency period are more likely to have diffuse injuries, paranoid symptoms, and auditory hallucinations (Fujii, 2002).

Other issues that complicate differential diagnosis include the age of onset, cognitive deficits, and evidence of a prodromal period. Age of onset for both psychosis secondary to TBI as well as schizophrenia averages around age 20-30, with onset before 20 years old being very rare (Guerreiro et al., 2009). TBI-related psychosis and schizophrenia both have identifiable prodromal periods marked by social withdrawal, affective disturbance, and paranoid behaviors. Finally, cognitive deficits are common to both disorders and are usually characterized by deficits in attention, memory, and executive function (Fujii, 2002).

In sum, TBI-related psychosis likely results from significant damage to frontal and temporal regions with associated dopaminergic dysfunction. Conversely, schizophrenia is most often marked by dopaminergic dysfunction, with enlarged ventricles being the most common clinical indicator on imaging (Zhang & Sachdev, 2003). While rare, psychosis resulting from brain injury can occur in either an open or closed injury, with injuries ranging from mild to severe. Diagnostic clarity is important for effective treatment, especially when considering type and dose of antipsychotic medication (Fujii, 2002). Moreover, investigation into psychosis secondary to TBI may elucidate on some of the inner-workings behind primary psychosis, especially with regard to intricate delusional systems. In all, these findings give further credence to the acknowledgement of schizophrenia as a neurobehavioral condition. Future research comparing insight in TBI-related psychosis to schizophrenia would be useful as insight is a strong prognostic indicator for all forms of psychosis.