New research of oral anomalies aids understanding of schizophrenia

Although the causes of schizophrenia are not well understood, health professionals in recent decades have been increasingly intrigued by the links between this complicated illness and human physical and neurological development. A recent study that I conducted with colleagues offers further indications that minor physical anomalies among individuals with schizophrenia support this neurodevelopmental model of the disease.

Facial anomalies seen in schizophrenia have been associated with aberrant brain development. It is suggested that craniofacial morphology and palatal abnormalities may be informative in elucidating the specific pathophysiology of schizophrenia, as there is a well-described interdependence between the developing brain and orofacial structures. It should be noted the oral palate is part of the bony structure that includes bones at which the base of the temporal lobe of the brain sits.

Gary Hack, DDS.

Our findings of physical orofacial differences in schizophrenia patients suggest the whole-body model of this illness is more accurate and also a more appropriate model to present to patients, their family members, and students.

In our study, lead author Dr. Kirkpatrick, chair of the department of psychiatry at the University of Nevada, Reno, School of Medicine, and I collaborated with an international team of colleagues to show that patients with a specific form of schizophrenia have a wider oral palate than people with other forms of the disease, as well as people without schizophrenia (Schizophrenia Bulletin, August 19, 2019).

Previous studies have indicated a high and narrow palate in patients with schizophrenia, but these studies were carried out with subjective assessment without quantitative measurements and were performed by examiners not blinded to the patient's diagnosis. However, recent studies that performed a quantitative assessment of the palatal dimensions in a blinded manner evidenced that the palates of patients with schizophrenia had significantly wider palates than controls without the disease.

Various terms have been utilized to describe the hard palate, which is difficult to assess clinically, owing to a previous lack of objective measurements. However, studies analyzing the correlation between defined measurements of the hard palate and anthropomorphic measurements of the skull and face have observed homogeneity among the measurements of the skull, face, and palate. In other words, the wide skull base found in schizophrenic patients would be consistent with having a wide palate.

The palate grows downward and forward from the anterior part of the skull base, such that individuals with wider skull bases also have broader palates. Developmentally, the anterior cranial base influences features of the palate.

Additionally, there is an increased orbital width or hypertelorism in patients with schizophrenia.

Dr. Kirkpatrick and colleagues in Schizophrenia Research (February 21, 2007) were the first authors to perform a quantitative assessment of palatal width in a blinded manner in schizophrenic patients. They showed that patients with schizophrenia had significantly wider palates than healthy controls.

Mehtap Delice and colleagues in Psychiatry Research (July 16, 2016) corroborated the research findings of Kirkpatrick and co-authors, again finding a significantly greater palatal width in schizophrenic patients compared with controls.

Recently, these two research groups, composed of dentists and psychiatrists, joined forces to form an interprofessional, international collaboration.

The causes of schizophrenia are not well understood, but in our recent study we shed light on the question of causation, with findings that may lead to a better understanding of the disorder.

The international, interprofessional team collaborated on oral palate research, comparing two groups of people with schizophrenia -- those with or without "deficit" features. Deficit schizophrenia is a form of the disease in which patients consistently experience at least two negative symptoms of the disease, such as amotivation or asociality. Deficit schizophrenia is thought to be a separate disease from other, nondeficit forms of schizophrenia.

"This palate difference in the deficit patients may reflect abnormal development during the prenatal period," Dr. Kirkpatrick stated. "A recognizable palate typically forms between weeks six and 17 during pregnancy, when most neurons travel from their birthplace to their final position in the brain."

These findings further open our minds to how many complex factors are at play as our minds and bodies develop, and to the holistic nature of human health that so many dentists and dental hygienists increasingly appreciate. Moreover, they may lead to future research that could one day reduce the number of individuals with neuropsychiatric conditions. In the meantime, I hope that together we can improve the dental experience for this population that already faces numerous social and financial barriers.

Gary Hack, DDS, is an associate professor in the department of advanced oral sciences and therapeutics at the University of Maryland School of Dentistry in Baltimore.

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