Neurological soft signs in non-psychotic first-degree relatives of patients with schizophrenia: a systematic review and meta-analysis

A step toward an objective quantification of subtle neurological signs in schizophrenia

Numerous reports have emphasized the value of neurological soft signs (NSS) as endophenotypic markers in schizophrenia. NSS also appear as useful prognostic predictors for functional outcome, response and tolerance to antipsychotics. Although several standardized scales have been proposed and offer fair inter-rater reliability, they still rely on the experience and accuracy of the investigators. This study was designed to assess NSS objectively. We evaluated 27 patients who met the Diagnostic and Statistical Manual, fourth edition (DSM-IV) criteria for schizophrenia and 15 healthy controls using a standardized examination encompassing a 23-item NSS scale as well as an assessment of parkinsonism and dyskinesia. Movements were then recorded using inertia sensors while the patients were performing a selection of motor items from the aforementioned scale (balance tasks, rapid alternative movements, rigidity). To our knowledge, this study is the first to provide an objective assessment of specific NSS in schizophrenia using inertial sensors. The results objectively demonstrate impairments in patients with schizophrenia when balance relies on proprioceptive information, with specific differences in groups of patients based on their NSS scores. Inertia sensors are promising, inexpensive and 'easy-to-use' tools that could improve the assessment of motor and sensory impairments in patients with schizophrenia in daily clinical practice, especially when the dysfunction is subtle.

Neurological soft signs and subcortical brain morphology in recent onset schizophrenia

BACKGROUND

Minor motor and sensory deficits or neurological soft signs (NSS) are frequently found in patients with schizophrenia at any stage of their illness. The thalamus and basal ganglia are accepted as being important for both motor control and integration of sensory input. However, whether NSS are related to alterations of these brain regions remains controversial.

METHOD

Twenty patients with recent onset schizophrenia were investigated using high-resolution magnetic resonance imaging (MRI) at 3 Tesla. NSS were examined on the Heidelberg Scale after remission of acute symptoms and related to both volumetric and shape measurements of thalamus, caudate nucleus, putamen, and globus pallidus, respectively. Age, education, medication and duration of illness were considered as potential confounders.

RESULTS

NSS were associated with structural alterations predominantly in the thalamus, the left caudate nucleus, and in the right globus pallidus. According to shape analyses these associations referred to regionally specific morphometric alterations rather than to global atrophy of the respective structures.

CONCLUSION

Our findings provide new insights into the association of NSS with brain morphometric alterations and lend further support to an involvement of multiple subcortical regions in schizophrenia.

Finding behavioral and network indicators of brain vulnerability

Resilience research has usually focused on identifying protective factors associated with specific stress conditions (e.g., war, trauma) or psychopathologies (e.g., post-traumatic stress disorder [PTSD]). Implicit in this research is the concept that resilience is a global construct, invariant to the unfavorable circumstances or the psychopathologies that may develop (i.e., the mechanisms underlying the resilience of an individual in all cases are expected to be similar). Here we contribute to the understanding of resilience—and its counterpart, vulnerability—by employing an approach that makes use of this invariant quality. We outline two main characteristics that we would expect from indicators of a vulnerable state: that they should appear across disorders regardless of specific circumstances, and that they should appear much before the disorder is evident. Next, we identify two sets of factors that exhibit this pattern of association with psychopathological states. The first was a set of “low-level” sensory, motor and regulatory irregularities that have been reported across the clinical literature; we suggest that these can serve as behavioral indicators of a vulnerable state. The second was the set of aberrations in network metrics that have been reported in the field of systems neuroscience; we suggest that these can serve as network indicators of a vulnerable state. Finally, we explore how behavioral indicators may be related to network indicators and discuss the clinical and research-related implications of our work.

Neurological soft signs in schizophrenia - The past, the present and the future

Clinical neurological abnormalities in patients with schizophrenia have been generally called "Neurological Soft Signs" (NSS). Studies have consistently shown increased NSS in patients with schizophrenia as compared to healthy persons. Early studies were limited by possible confounds of prior neuroleptic medications and illness chronicity. Studies in first episode never treated schizophrenia patients have addressed these confounds. The clinical significance of these findings and the correlation with cognitive dysmetria is the focus of the current review. Relevant literature was obtained using PUBMED and MEDLINE search (1980-2008) and a direct search of reference list of pertinent journal articles. In a 2003 study, neuroleptic-naive schizophrenia patients had significantly more NSS than controls. Patients who were more neurologically impaired had more negative symptoms. Higher NSS scores in treatment-naive schizophrenia patients and the absence of correlation between NSS and illness duration lends support to a neurodevelopmental pathogenesis for schizophrenia. The finding of incoordination and cerebellar signs in most studies also supports the "cognitive dysmetria" explanatory model for schizophrenia. A significant subgroup of patients with schizophrenia may have more neuropathological abnormalities, which predisposes them for a more severe and chronic course of illness. These patients may potentially be identified by clinical neurological examination, which might be very important for prognostication and evolving better methods of treatment for these patients. NSS, by themselves or as a composite index with other neurobiological parameters, hold potential as a candidate endophenotype for schizophrenia.

A systematic meta-review grading the evidence for non-genetic risk factors and putative antecedents of schizophrenia

INTRODUCTION

Identifying the relative strength of evidence associated with non-genetic risk factors and putative antecedents of schizophrenia will guide research and may inform the design of early detection and intervention strategies.

AIMS

To present and quality assess current evidence for non-genetic risk factors and putative antecedents derived from well-conducted systematic reviews that report pooled data.

METHOD

Medline, Embase, CINAHL, Current Contents, and PsycINFO databases were searched systematically, and supplemented by hand searching. Review reporting quality was assessed using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist, review methodology was assessed using the Assessment of Multiple Systematic Reviews (AMSTAR) checklist, and evidence quality was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

RESULTS

Twenty-four reviews met inclusion criteria. The risk factors with the highest quality evidence, reporting medium effect sizes, were advanced paternal age, obstetric complications, and cannabis use. The strongest evidence among the putative antecedents was identified for motor dysfunction and low IQ.

CONCLUSIONS

More research is required that applies sound methodological practices, taking into consideration specificity for schizophrenia and possible confounding factors, to robustly identify the non-genetic risk factors and putative antecedents of schizophrenia.

Do we have any solid evidence of clinical utility about the pathophysiology of schizophrenia?

A diagnosis of schizophrenia, as in most of psychiatric practice, is made largely by eliciting symptoms with reference to subjective, albeit operationalized, criteria. This diagnosis then provides some rationale for management. Objective diagnostic and therapeutic tests are much more desirable, provided they are reliably measured and interpreted. Definite advances have been made in our understanding of schizophrenia in recent decades, but there has been little consideration of how this information could be used in clinical practice. We review here the potential utility of the strongest and best replicated risk factors for and manifestations of schizophrenia within clinical, epidemiological, cognitive, blood biomarker and neuroimaging domains. We place particular emphasis on the sensitivity, specificity and predictive power of pathophysiological indices for making a diagnosis, establishing an early diagnosis or predicting treatment response in schizophrenia. We conclude that a number of measures currently available have the potential to increase the rigour of clinical assessments in schizophrenia. We propose that the time has come to more fully evaluate these and other well replicated abnormalities as objective potential diagnostic and prognostic guides, and to steer future clinical, therapeutic and nosological research in this direction.

Neurological soft signs in individuals with schizotypal personality features

OBJECTIVE

The current study attempted to examine the prevalence of neurological soft signs and their relationships with schizotypal traits in individuals with psychometrically defined schizotypal personality disorder (SPD) features.

METHOD

Sixty-four individuals with SPD-proneness and 51 without SPD-proneness were recruited for the present study. The soft signs subscales of the Cambridge Neurological Inventory were administered to all participants; the Schizotypal Personality Questionnaire (SPQ) was administered to SPD-proneness and non-SPD-proneness participants.

RESULTS

The SPD-proneness participants demonstrated significantly higher prevalence of soft signs than those without SPD-proneness. SPQ subscales were significantly associated with ratings of motor coordination, sensory integration and total soft signs.

CONCLUSION

These findings suggest that neurological soft signs are trait markers of schizophrenia.