The capacity for imagery, enabling us to visualise absent items and events, is a ubiquitous feature of our experience. This paper describes the case of a patient, MX, who abruptly lost the ability to generate visual images. He rated himself as experiencing almost no imagery on standard questionnaires, yet performed normally on standard tests of perception, visual imagery and visual memory. These unexpected findings were explored using functional MRI scanning (fMRI). Activation patterns while viewing famous faces were not significantly different between MX and controls, including expected activity in the fusiform gyrus. However, during attempted imagery, activation in MX's brain was significantly reduced in a network of posterior regions while activity in frontal regions was increased compared to controls. These findings are interpreted as suggesting that MX adopted a different cognitive strategy from controls when performing the imagery task. Evidence from experimental tasks thought to rely on mental imagery, such as the Brooks' matrices and mental rotation, support this interpretation. Taken together, these results indicate that successful performance in visual imagery and visual memory tasks can be dissociated from the phenomenal experience of visual imagery.

Objective Central nervous system (CNS) features in children with permanent neonatal diabetes (PNDM) due to KCNJ11 mutations have a major impact on affected families. Sulfonylurea therapy achieves outstanding metabolic control, but only partial improvement in CNS features. The effects of KCNJ11 mutations on the adult brain and their functional impact are not well described. We aimed to characterise the CNS features in adults with KCNJ11 PNDM, compared to adults with INS PNDM. Research Design and Methods Adults with PNDM due to KCNJ11 mutations (n=8) or INS mutations (n=4) underwent a neurological examination, and completed standardised neuropsychological tests/questionnaires about development/behavior. Four individuals in each group underwent a brain MRI scan. Test scores were converted to Z-scores using normative data, and outcomes compared between groups. Results In individuals with KCNJ11 mutations, neurological examination was abnormal in 7/8; predominant features were subtle deficits in coordination/motor sequencing. All had delayed developmental milestones and/or required learning support/special schooling. Half had features and/or a clinical diagnosis of autism spectrum disorder. KCNJ11 mutations were also associated with impaired attention, working memory and perceptual reasoning, and reduced IQ (median IQ KCNJ11 vs INS mutations 76 vs 111, p=0.02). However, no structural brain abnormalities were noted on MRI. The severity of these features was related to the specific mutation and they were absent in individuals with INS mutations. Conclusions KCNJ11 PNDM is associated with specific CNS features which are not due to long-standing diabetes, persist into adulthood despite sulfonylurea therapy, and represent the major burden from KCNJ11 mutations.

The SCA 8 expansion is associated with ataxia in Scotland. The disorder is associated with a dysexecutive syndrome.

The cerebellar cognitive affective syndrome (CCAS) was first described by Schmahmann and Sherman as a constellation of symptoms including dysexecutive syndrome, spatial cognitive deficit, linguistic deficits and behavioural abnormalities in patients with a lesion in the cerebellum with otherwise normal brain. Neurosurgical patients with cerebellar tumours constitute one of the cohorts in which the CCAS has been described. In this paper, we present a critical review of the literature of this syndrome in neurosurgical patients. Thereafter, we present a prospective clinical study of 10 patients who underwent posterior fossa tumour resection and had a detailed post-operative neuropsychological, neuropsychiatric and neuroradiological assessment. Because our findings revealed a large number of perioperative neuroradiological confounding variables, we reviewed the neuroimaging of a further 20 patients to determine their prevalence. Our literature review revealed that study design, methodological quality and sometimes both diagnostic criteria and findings were inconsistent. The neuroimaging study (pre-operative, n = 10; post-operative, n = 10) showed very frequent neuroradiological confounding complications (e.g. hydrocephalus; brainstem compression; supratentorial lesions and post-operative subdural hygroma); the impact of such features had largely been ignored in the literature. Findings from our clinical study showed various degree of deficits in neuropsychological testing (n = 1, memory; n = 3, verbal fluency; n = 3, attention; n = 2, spatial cognition deficits; and n = 1, behavioural changes), but no patient had full-blown features of CCAS. Our study, although limited, finds no robust evidence of the CCAS following surgery. This and our literature review highlight a need for guidelines regarding study design and methodology when attempting to evaluate neurosurgical cases with regard to the potential CCAS.

BackgroundChildren with neonatal diabetes often present with diabetic ketoacidosis and hence are at risk of cerebral oedema and subsequent long‐term neurological deficits. These complications are difficult to identify because neurological features can also occur as a result of the specific genetic aetiology causing neonatal diabetes.Case reportsWe report two cases of neonatal diabetes where ketoacidosis‐related cerebral oedema was the major cause of their permanent neurological disability. Case 1 (male, 18 years, compound heterozygous ABCC8 mutation) and case 2 (female, 29 years, heterozygous KCNJ11 mutation) presented with severe diabetic ketoacidosis at 6 and 16 weeks of age. Both had reduced consciousness, seizures and required intensive care for cerebral oedema. They subsequently developed spastic tetraplegia. Neurological examination in adulthood confirmed spastic tetraplegia and severe disability. Case 1 is wheelchair‐bound and needs assistance for transfers, washing and dressing, whereas case 2 requires institutional care for all activities of daily living. Both cases have first‐degree relatives with the same mutation with diabetes, who did not have ketoacidosis at diagnosis and do not have neurological disability.DiscussionKetoacidosis‐related cerebral oedema at diagnosis in neonatal diabetes can cause long‐term severe neurological disability. This will give additional neurological features to those directly caused by the genetic aetiology of the neonatal diabetes. Our cases highlight the need for increased awareness of neonatal diabetes and earlier and better initial treatment of the severe hyperglycaemia and ketoacidosis often seen at diagnosis of these children.

Transcranial Doppler ultrasound has been used to detect cerebral emboli after hip arthroplasty. The cognitive effects of these embolic events are unclear. The aim of this study was to assess cognitive change after primary cemented hip arthroplasty using a range of neuropsychological tests and to measure intraoperative cerebral embolic load. Twenty primary cemented total hip arthroplasties underwent a series of cognitive tests before and at four days after surgery. A range of validated tests assessed: global cognitive function; verbal fluency and speed; immediate and delayed memory recall; attention and mental processing speeds. Intra-operative transcranial Doppler ultrasound monitoring of the middle cerebral artery for embolic signals was also performed. A one-sample Wilcoxon signed-rank test compared median cognitive results post-pre surgery and a Mann-Whitney U test established if there was a cognitive difference between those patients who had detectable cerebral emboli and those who did not. Scatter plot graphs were also used to establish any correlation between the embolic load and clinical cognitive dysfunction. A significant (p<0.01) difference was noted in specific tests assessing mental processing speed, visual searching and sustained and divided attention following surgery. Intra-operative cerebral embolic signals were detected in 11 out of 20 patients and the majority occurred with femoral component cementation and hip reduction. There was no difference in cognitive dysfunction between those patients who had detectable cerebral embolic signals and those who did not and there appeared to be no direct correlation between the size of the embolic load and the level of cognitive dysfunction.

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