Patients with Parkinson's disease (PD) and essential tremor (ET) can experience deficits in executive functioning (EF) secondary to abnormalities in fronto-striatal and cerebellar-frontal pathways respectively. The assessment of EF can be confounded in these patients due to motor difficulties and slowed processing speed. Thus, instruments which do not require speeded motor responses are potentially attractive in this population. The Neuropsychological Assessment Battery-Categories Test (NABCAT) is one such instrument. This study evaluated the convergent and divergent validity of this measure as well as its diagnostic accuracy in comparison to other commonly administered tests. Records for 28 patients with PD and/or ET who presented for evaluation pre-deep brain stimulation surgery were analyzed. The NABCAT had modest correlations with other measures of EF, as well as memory. However, it demonstrated relatively poor sensitivity and modest specificity to executive dysfunction. The NABCAT did not demonstrate adequate psychometric properties to replace traditional measures of EF in this population; however, it may have utility as a screening instrument for more significant dysfunction.
Keywords: Parkinson’s disease; executive functioning; neuropsychological testing, essential tremor; sensitivity and specificity..