Fifty Percent Prevalence of Extracampine Hallucinations in Parkinson’s Disease Patients

Extracampine hallucinations (EH), the sense of a presence or fleeting movement in the absence of an associated visual percept, have been reported in Parkinson’s disease (PD) patients but their prevalence, characteristics and temporal relationship to visual hallucinations (VH) remain unclear. Given that VH are predictive of cognitive impairment in PD, improved understanding of EH may have significant prognostic implications. The objective of this study was to evaluate the prevalence and characteristics of EH in a large unselected population with PD and to assess the temporal relationship between EH, VH and memory decline. Cross-sectional data were collected using a questionnaire circulated to 414 PD patients via an online patient community. Data were obtained regarding the occurrence, timing and characteristics of VH and EH and symptoms of PD, disease duration, disease severity and medication history. 50.4% of respondents reported EH and 15.5% reported VH. EH were typically experienced alongside, rather than behind, the individual (p<0.001) without clear lateralisation (p=0.438), and were more likely to be of unfamiliar presences (p<0.001). The occurrence of EH was associated with Hoehn and Yahr score (p=0.002) but not disease duration (p=0.158). EH onset was associated with VH onset (p=0.046) and occurred after the onset of anosmia (p<0.001), cognitive decline (p=0.002) and sleep disturbance (p=0.002). The reported prevalence of EH in PD patients was threefold greater than that of VH, with similar timings of onset, suggesting that EH are under-recognised and under-reported. Further work is needed to determine whether EH are predictive of cognitive decline

Nitrous oxide-induced motor-predominant axonal peripheral neuropathy: A phenotype distinct from isolated vitamin B12 deficiency

Highlights: N2O toxicity and B12 deficiency both cause a sensory predominant myeloneuropathy. N2O abuse may also lead to a selectively severe motor axonal peripheral neuropathy. This motor neuropathy phenotype may be related to N2O direct neural toxicity. In-vivo measures of motor axonal dysfunction are more pronounced in N2O abuse

Sheehan Syndrome Associated With Raised Intracranial Pressure

Intracranial hypertension (IH) has been associated with hypocortisolism caused by either primary adrenocortical insufficiency or corticosteroid withdrawal. The authors describe a case of IH in association with Sheehan syndrome (SS) in a postpartum 29-year-old woman. The clinical manifestations of IH resolved with corticosteroid replacement. This case supports a causal role of hypocortisolism in IH. The authors are unaware of previous reports of hypocortisolism caused by SS leading to IH

Allocentric Spatial Memory Testing Predicts Conversion from Mild Cognitive Impairment to Dementia: An Initial Proof-of-Concept Study

The hippocampus is one of the first regions to exhibit neurodegeneration in Alzheimer’s disease (AD), and knowledge of its role in allocentric spatial memory may therefore aid early diagnosis of AD. The 4 Mountains Test (4MT) is a short and easily administered test of spatial memory based on the cognitive map theory of hippocampal function as derived from rodent single cell and behavioral studies. The 4MT has been shown in previous cross-sectional studies to be sensitive and specific for mild cognitive impairment (MCI) due to AD. This report describes the initial results of a longitudinal study testing the hypothesis that allocentric spatial memory is predictive of conversion from MCI to dementia. Fifteen patients with MCI underwent baseline testing on the 4MT in addition to CSF amyloid/tau biomarker studies, volumetric MRI and neuropsychological assessment including the Rey Auditory Verbal Learning Test (RAVLT) and Trail Making Test “B” (TMT-B). At 24 months, 9/15 patients had converted to AD dementia. The 4MT predicted conversion to AD with 93% accuracy (Cohen’s d = 2.52). The predictive accuracies of the comparator measures were as follows: CSF tau/β-amyloid1–42 ratio 92% (d = 1.81), RAVLT 64% (d = 0.41), TMT-B 78% (d = 1.56), and hippocampal volume 77% (d = 0.65). CSF tau levels were strongly negatively correlated with 4MT scores (r = −0.71). This proof-of-concept study provides initial support for the hypothesis that allocentric spatial memory testing is a predictive cognitive marker of hippocampal neurodegeneration in pre-dementia AD. The 4MT is a brief, non-invasive, straightforward spatial memory test and is therefore ideally suited for use in routine clinical diagnostic practice. This is of particular importance given the current unmet need for simple accurate diagnostic tests for early AD and the ongoing development of potential disease-modifying therapeutic agents, which may be more efficacious when given earlier in the disease course. By applying a test based on studies of hippocampal function in rodents to patient populations, this work represents the first step in the development of translatable biomarkers of hippocampal involvement in early AD for use in both animal models and human subjects