Faculty Bibliography

INTRODUCTION:Validity indicators embedded within standard neuropsychological tests have received increasing attention as more efficient measures for sampling performance validity throughout an evaluation. This cross-sectional study examined multiple performance validity tests (PVTs) embedded in the Wechsler Adult Intelligence Scale-IV (WAIS-IV) Working Memory (WMI) and Processing Speed (PSI) Indices for detecting invalid test performance. METHOD:This cross-sectional study examined data from a mixed clinical neuropsychiatric sample of 110 patients referred for outpatient evaluation. The sample was composed of 85 patients with valid neuropsychological performance and 25 with invalid performance based on multiple independent criterion PVTs. Among the patients with valid performance, 54% were cognitively impaired, whereas 46% were cognitively unimpaired. RESULTS: CONCLUSION:Overall, results indicated that embedded WAIS-IV WMI and PSI are useful embedded PVTs in conditions in which cognitive impairment is not expected; however, these embedded PVTs demonstrated questionable utility among patients with cognitive impairment due to poor sensitivity, if adequate specificity is maintained, suggesting limited efficacy among patients with cognitive impairment due to risk of false-positive classification.

A patient diagnosed with developmental delay, intellectual disability, and autistic and obsessive-compulsive symptoms was found to have a posterior fossa arachnoid cyst (PFAC) compressing the cerebellum. The patient was referred to our Ataxia Unit for consideration of surgical drainage of the cyst to improve his clinical constellation. This scenario led to an in-depth analysis including a literature review, functional resting-state MRI analysis of our patient compared to a group of controls, and genetic testing. While it is reasonable to consider that there may be a causal relationship between PFAC and neurodevelopmental or psychiatric symptoms in some patients, there is also a nontrivial prevalence of PFAC in the asymptomatic population and a significant possibility that many PFAC are incidental findings in the context of primary cognitive or psychiatric symptoms. Our functional MRI analysis is the first to examine brain function, and to report cerebellar dysfunction, in a patient presenting with cognitive/psychiatric symptoms found to have a structural abnormality compressing the cerebellum. These neuroimaging findings are inherently limited due to their correlational nature but provide unprecedented evidence suggesting that cerebellar compression may be associated with cerebellar dysfunction. Exome gene sequencing revealed additional etiological possibilities, highlighting the complexity of this field of cerebellar clinical and scientific practice. Our findings and discussion may guide future investigations addressing an important knowledge gap-namely, is there a link between cerebellar compression (including arachnoid cysts and possibly other forms of cerebellar compression such as Chiari malformation), cerebellar dysfunction (including fMRI abnormalities reported here), and neuropsychiatric symptoms?