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AbstractObsessive–compulsive disorder (OCD) is a chronic and disabling mental disorder characterized by the presence of obsessions and/or compulsions that cause major distress and impair important areas of functioning. About 9 out of 10 patients with OCD have comorbid psychiatric diagnoses. A high proportion of clinically diagnosed OCD patients fulfill diagnostic criteria of a schizophrenia spectrum disorder, to the point that significant evidence in the literature supports the existence and the clinical relevance of a schizo-obsessive spectrum of disorders, including schizotypal personality disorder (SPD) with OCD (schizotypal OCD). In this paper, we provide a brief but comprehensive analysis of the literature on the clinical coexistence between OCD and SPD. The clinical validity of the so-called schizotypal OCD is analyzed through a comprehensive investigation of the relationship between SPD features and obsessive–compulsive phenomena in clinical OCD samples. This review describes the potential connections between OCD and SPD on the epidemiological, sociodemographic, psychopathological, and clinical levels. SPD is commonly observed in OCD patients: about 10% of OCD patients have a full categorical diagnosis of SPD. Early clinical identification of SPD features—and, more generally, of psychotic features and personality disorders—in OCD patients is strongly recommended. In fact, a proper and early diagnosis with early treatment may have benefits for prognosis. However, although schizotypal OCD seems to have clinical and predictive validity, further neurobiological and genetic studies on etiological specificity are warranted.

Musical hallucinations are uncommon phenomena characterized by intrusive and frequently distressful auditory musical percepts without an external source, often associated with hypoacusis, psychiatric illness, focal brain lesion, epilepsy, and intoxication/pharmacology. Their physiological basis is thought to involve diverse mechanisms, including “release” from normal sensory or inhibitory inputs as well as stimulation during seizures, or they can be produced by functional or structural disorders in diverse cortical and subcortical areas. The aim of this review is to further explore their pathophysiology, describing the functional neuroimaging findings regarding musical hallucinations. A literature search of the PubMed electronic database was conducted through to 29 December 2015. Search terms included “musical hallucinations” combined with the names of specific functional neuroimaging techniques. A total of 18 articles, all clinical case reports, providing data on 23 patients, comprised the set we reviewed. Diverse pathological processes and patient populations with musical hallucinations were included in the studies. Converging data from multiple studies suggest that the superior temporal sulcus is the most common site and that activation is the most common mechanism. Further neurobiological research is needed to clarify the pathophysiology of musical hallucinations.