Neurological soft signs (NSS) are abnormalities identified by clinical examination. They are referred to as ‘soft’ because they are not related to a localised pathological lesion and are not part of a well-defined neurological syndrome.

NSS can be grouped into three categories: integrative sensory functioning, motor coordination, and complex motor sequencing. Integrative sensory functioning includes deficits in bilateral extinction (difficulty perceiving stimuli when presented to both hemispheres simultaneously), impaired audio-visual integration, agraphaesthesia (inability to recognise by touch letters and numbers drawn on the skin) and astereognosis (inability to identify an object by touch without visual input). Motor coordination involves general coordination, intention tremor, finger thumb opposition, balance, and gait. Motor sequencing measures complex motor tasks, such as repetitive alternating hand positions. Abnormalities in eye movements and developmental reflexes may also be apparent.

What is the evidence for NSS in people with bipolar disorder?

Moderate quality evidence suggests a large effect of more NSS in people with bipolar disorder than controls. This effect remained large in the subgroup analyses of bipolar disorder type, in euthymia patients, and in task type. Tasks included sensory integration, motor coordination, or motor sequencing. There were no moderating effects of age, sex, duration of illness, age of onset, or antipsychotic use.

Moderate to high quality evidence found a medium-sized effect of less NSS in people with bipolar disorder than in people with schizophrenia. Subgroup analyses showed only motor coordination scores were significantly lower in bipolar disorder. There were also no significant differences between people with bipolar disorder with psychotic symptoms, and people with schizophrenia. There were no moderating effects of age, sex, duration of illness or age of onset.

September 2021

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Neurological soft signs (NSS) are neurological abnormalities that can be identified by clinical examination using valid and reliable testing measures. They are referred to as ‘soft’ because they not related to a specific brain area, or part of a defined syndrome. Categories of NSS are commonly grouped into three categories; integrative sensory functioning, motor coordination, and complex motor sequencing. Integrative sensory functioning includes impairments in sensory perception such as audio-visual integration or tactile recognition. Motor coordination involves general coordination, balance and gait. Complex motor sequencing involves complex motor tasks, such as repetitive alternating hand positions.

What is the evidence for NSS?

Moderate to high quality evidence suggests medium to large effects of increased NSS in people with schizophrenia or first-episode psychosis compared to people without a psychiatric disorder (controls). There is a small and less widespread effect when comparing people with a first-degree relative with schizophrenia to controls. Compared to people with bipolar disorder and no psychotic symptoms, moderate to high quality evidence shows a small to medium-sized effect of more NSS in people with schizophrenia on motor coordination tasks only.

There are medium-sized associations between increased NSS scores and increased symptom severity and poorer cognitive performance in people with schizophrenia. Both people with remitting or chronic schizophrenia showed improvements in NSS over time, although remitting symptoms were associated with greatest NSS improvements. Increased severity of NSS in people with schizophrenia was associated with; reduced activation of the basal ganglia and inferior frontal cortex, increased activation of the superior temporal gyrus, reduced grey matter volume in the precentral and inferior frontal gyri and thalamus, and reduced white matter volume in the middle temporal and cerebellum regions.

February 2022

Image: ©Aleksey Khripunkov – stock.adobe.com

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