Raphe Nuclei Echogenicity and Diameter of Third Ventricle in Schizophrenia Measured by Transcranial Sonography

Introduction: Serotonergic system hyperactivity at 5-HT2A receptors on glutamate neurons in the cerebral cortex is one of the pathways that is theoretically linked to psychosis. In addition to neurotransmitter dysfunction, volumetric studies have revealed the loss of cortical gray matter and ventricular enlargement in patients with schizophrenia, although there is no case-control research on patients with schizophrenia to evaluate echogenicity of raphe nuclei (RN) or diameter of the third ventricle (DTV). To address these issues, the present study assessed midbrain RN, as the main source of brain serotonin, and DTV, as an index of atrophy, by transcranial sonography (TCS) in a group of patients with schizophrenia.

Methods: Thirty patients with schizophrenia and 30 controls were assessed by TCS for RN echogenicity and DTV. TCS was done through a temporal bone window via a phased-array ultrasound using a 2.5 MHz transducer in a depth of 14-16 cm. RN echogenicity was assessed by a semi-quantitative visual scale and DTV was measured in the thalamic plane.

Results: Twenty-three patients (76.5%) and 15 controls (50 %) showed hypoechogenicity of RN, which was marginally significant (P=0.06). DTV was on average larger in the experimental group (0.388 cm vs 0.234 cm, P<0.001).

Conclusion: Increased DTV in patients with schizophrenia is consistent with previous neuroimaging findings. However, marginally lower echogenicity of midbrain RN on TCS in schizophrenia is a new finding that supports the serotonin hypothesis of schizophrenia.

Highlights: 30 patients with schizophrenia and 30 controls were assessed by TCS for RN echogenicity and diameter of the third ventricle (DTV).23 patients (76.5%) and 15(50 %) controls showed hypoechogenicity of RN which was marginally significant (P=0.06)DTV was in average larger in the patient's group (0.388 cm vs 0.234 cm, P<0.001).Increased DTV in the patients with schizophrenia is consistent with previous neuroimaging findingsMarginally lower echogenicity of midbrain RN on TCS in schizophrenia is a new finding that supports the serotonin hypothesis of schizophrenia.

Plain language summary: Schizophrenia is a disabling psychiatric disorder. Various neurotransmitters have a role in the pathophysiology of schizophrenia including Serotonin and dopamine. This study assessed the echogenicity of raphe nuclei (RN), as the main source of brain serotonin, and the diameter of the third ventricle (DTV), as an index of atrophy, by transcranial sonography (TCS) method in 30 patients with schizophrenia and 30 healthy controls. Based on the results, 23 patients (76.5%) and 15 controls (50%) showed decreased echogenicity of RN. There was a significant difference between the two groups in terms of the echogenicity of RN. Moreover, the DTV diameter was significantly larger in patients compared to controls.