Neuropsychology and MRI Observational Study In An Adult Sickle Cell Disease Population In South East London

Abstract 2642

We studied 36 patients attending the sickle cell clinic in our large adult population of over 600 patients. These patients presented to the sickle psychology service because they had a past history of a stroke, or presented with concerns about memory. An MRI brain scan and neuropsychological testing (including tests for IQ, processing speed, executive function and memory) were performed on each patient. The data were organised into four groups in terms of severity of MRI abnormalities: normal MRI n=13; silent cerebral infarcts (subcortical punctate small vessel cerebrovascular disease) n= 11; severe infarcts as an adult n=8; and severe infarcts as a child n=4. The majority of patients with a history of stroke had evidence of large vessel infarcts as well as features of deep watershed ischaemia seen in large vessel (distal internal carotid artery) disease. These groups did not differ significantly in terms of gender, phenotype, age and mood. Cognitive impairments were more prevalent in the severe infarct groups but were also found in patients with silent cerebral infarcts and normal MRIs. Executive functioning and processing speed deficits were evident in all groups but were more severe in the silent cerebral infarct and severe infarct groups. Chi-squared tests for trend showed that the following test scores tended to reduce as MRI abnormalities increased: Full-Scale IQ (p=0.016), Processing Speed Index (p=0.015), Trail Making Test A (p=0.014), Trail Making Test B (p=0.018), and FAS Verbal Fluency Test (p=0.006). This suggests that executive functioning, processing speed and full-scale IQ are particularly vulnerable to the effects of MRI abnormalities in this patient population. Although the cognitive impairments were more severe in the groups with abnormal MRIs, there was significant cognitive impairment in some patients with normal MRIs, suggesting that other factors are also causative of cognitive impairments. These factors may include physiological causes such as impaired perfusion, and psychosocial factors such as disruption to education. These results agree with a recent US study (Vichinsky et al, 2010, JAMA, 303, 1823–1831) showing cognitive impairment in patients with normal MRI scans which implies that MRI is not an adequate screening tool to identify patients with cognitive impairment. This study has important clinical implications in terms of how cognitive deficits can affect the effectiveness of patient – health care professional consultations, patients' ability to manage their SCD and adhere to medication and health care advice. It is important therefore to identify patients with SCD who have such cognitive impairments so appropriate support can be offered.