Clinical significance of neurological soft signs in schizophrenia: factor analysis of the Neurological Evaluation Scale.
BACKGROUND
Nonlocalizing neurologic deficits detectable by clinical evaluation-"soft signs"-are a robust finding in patients diagnosed with schizophrenia, but their conceptual and neuroanatomical correlates remain unclear. The purpose of this study was to evaluate the organization of these deficits and their clinical correlates using the Neurological Evaluation Scale (NES).


METHODS
Ninety-three male veterans with schizophrenia and schizoaffective disorder were evaluated using a detailed clinical assessment that included the NES, the Extrapyramidal Symptom Rating Scale, the Abnormal Involuntary Movement Scale (AIMS), the Barnes Akathisia Scale, the Positive and Negative Syndrome Scale, the Wisconsin Card Sorting Test (WCST), the Schedule for the Deficit Syndrome (SDS), and the Digit Symbol Substitution Task (DSST).


RESULTS
Four factors explained 73% of the variance and had distinct clinical and neuropsychological correlates. Factor 1 reflected deficits involved with memory and sensory integration, and was associated with lower PANSS positive and higher AIMS scores. Factor 2 reflected impairments in motor control, and was associated with lower intelligence, more cognitive deficits, and deficit-syndrome schizophrenia. Factor 3 was related to lower intelligence and more perseverative errors on the WCST. Factor 4 was related to increasing age, more extrapyramidal symptoms, more perseverative errors, and worse scores on the DSST.


CONCLUSIONS
Neurologic deficits in schizophrenia have an intrinsic organization that appears to have clinical significance, highlighting the continued utility of the NES in studies of neurological deficits in schizophrenia patients. The theoretical underpinning of this organization remains unclear.
Sewell
R Andrew
RA
Department of Psychiatry, Yale University School of Medicine, New Haven, CT, USA. asewell71@gmail.com
Perry
Edward B
EB
Karper
Laurence P
LP
Bell
Morris D
MD
Lysaker
Paul
P
Goulet
Joseph L
JL
Brenner
Louise
L
Erdos
Joseph
J
d'Souza
D Cyril
DC
Seibyl
John P
JP
Krystal
John H
JH
D000328:Adult; D000367:Age Factors; D003071:Cognition; D005163:Factor Analysis, Statistical; D005260:Female; D006801:Humans; D007360:Intelligence; D008297:Male; D008568:Memory; D008875:Middle Aged; D009068:Movement; D009460:Neurologic Examination; D009483:Neuropsychological Tests; D011569:Psychiatric Status Rating Scales; D011594:Psychometrics; D011618:Psychotic Disorders / Q000503:physiopathology* / Q000523:psychology*; D012559:Schizophrenia / Q000503:physiopathology*; D012565:Schizophrenic Psychology; D012677:Sensation