Pupil dilatation assay by tropicamide is modulated by apolipoprotein E epsilon 4 allele dosage in Alzheimer's disease

Enhancing Diagnostic Accuracy of aMCI in the Elderly: Combination of Olfactory Test, Pupillary Response Test, BDNF Plasma Level, and APOE Genotype

Background. Amnestic Mild Cognitive Impairment (aMCI) often progresses to Alzheimer's disease. There are clinical markers and biomarkers to identify the degenerative process in the brain. Objectives. To obtain the diagnostic values of olfactory test, pupillary response to tropicamide 0.01%, BDNF plasma level, and APOE ε4 in diagnosing aMCI. Methods. Cross-sectional, comparative analysis. Results. There were 109 subjects enrolled (aMCI: 51, normal cognition: 58) with age 64 ± 5.54 years. For diagnosing aMCI, cut-off point for the olfactory score was <7 out of 10 and >22% for pupil dilatation response. Low BDNF plasma level was related significantly with olfactory deficits and aMCI (P < 0.05). Four of five subjects with homozygote e4 presented with multiple-domain aMCI. This group displayed the lowest means of olfactory score and the highest means of pupillary hypersensitivity response (P < 0.0001). Combination of olfactory deficit and pupillary hypersensitivity response in detection of aMCI was beneficial with Sp 91% and PPV 87%. In conjunction with clinical markers, BDNF plasma level and presence of APOE e4+ improved Sp and PPV. Conclusions. Combination of olfactory test and pupillary response test was useful as diagnostic tool in aMCI. In conjunction with clinical markers, low level of BDNF plasma and presence of APOE e4 improved the diagnostic value.

Pupil response biomarkers distinguish amyloid precursor protein mutation carriers from non-carriers

CONTEXT

Alzheimer's disease (AD) is usually only diagnosed many years after pathology begins. Earlier detection would allow emerging interventions to have a greater chance to preserve healthy brain function. A rare form of Alzheimer's disease, caused by autosomal-dominant mutations, affects carriers with 100% certainty and at a younger age specific to their mutation. Studying families with these mutations allows a unique investigation of the temporal sequence of biomarker changes in Alzheimer's disease.

OBJECTIVE

To determine whether the pupil flash response (PFR), previously reported to be altered in sporadic Alzheimer's disease, is different in pre-symptomatic mutation carriers.

DESIGN

Researchers blinded to participant mutation status collected pupil response data from cognitively normal participants in the Dominantly Inherited Alzheimer's Network (DIAN) Study during 2010-2011.

SETTING

The pupil response was examined at the McCusker Alzheimer's Research Foundation in Perth, Western Australia.

PARTICIPANTS

Participants were from a single family harboring an Amyloid-Beta Precursor Protein genetic mutation (APPGlu693Gln). Six carriers and six non-carriers were available for pupil testing (age 43.0±8.3 years old, 2 males and 10 females, 4 with hypertension).

MAIN OUTCOME MEASURE

Pupil response parameter comparison between mutation carriers and non-carriers.

RESULTS

75% recovery time was longer in mutation carriers (p<0.0003, ROC AUC 1.000, Sensitivity 100%, Specificity 100%) and percentage recovery 3.5 seconds after stimulus was less in mutation carriers (p<0.006, ROC AUC 1.000, Sensitivity 100%, Specificity 100%).

CONCLUSIONS

PFR changes occur pre-symptomatically in autosomal dominant AD mutation carriers, supporting further investigation of PFR for early detection of AD.

Sensitive pupil response of early-onset alzheimer's patients to a dilute mixture of cholinergic antagonist and α-Adrenergic stimulant

To investigate possible differences in pupil dilation and light reflex in Alzheimer's disease patients that can be attributed to the age of onset of the disease, a statistical comparison was made of pupil dilation and light reflex among early- and late-onset Alzheimer's disease, Down syndrome, and patients with vascular dementia, and normal controls. The subjects included 53 probable Alzheimer's disease outpatients, including both early-onset type (AD: n=21) and late-onset type (SD: n=32). They were compared with normal controls (n=15), Down syndrome patients (DS: n=6), and patients with vascular dementia (VD: n=9). All subjects and controls were dark-eyed Japanese. Pupil dilation and light reflex were tested in 21 AD and 32 SD patients, and were compared with those in the control subjects; 6 DS and 9 VD patients. The measured maximum increase in pupil diameter after instilling a mixture of anticholinergic and α -adrenergic stimulating drugs (Midrin-P®), in one eye was significantly greater in AD and DS than in the controls. However, there was no difference among SD, VD, and controls, suggesting a stronger pupil response to these drugs in AD than in SD. Pupil movement in response to light became significantly smaller and faster after instillation of the drugs in Alzheimer's disease patients. The above findings may be useful for the early detection of Alzheimer's disease.

Pupillary cholinergic hypersensitivity predicts cognitive decline in community dwelling elders

Previous research demonstrated that it is possible to distinguish patients with probable Alzheimer's disease from age-matched controls based on an exaggerated pupil dilation response to dilute tropicamide. The research reported here employed a prospective longitudinal design to follow over time (2-4 years) a sample of 55 community dwelling elders with and without an exaggerated pupil response using the pupil assay and a comprehensive battery of neuropsychological tests sensitive to pre-clinical AD. Discrete time survival modeling was used to assess the ability of the assay to predict a pattern of cognitive decline consistent with early AD. Analysis showed that there is an increased risk (odds ratio of 3) with a hypersensitive pupil response (>/=13% increase in pupil diameter over baseline diameter) for developing significant cognitive impairment in areas of memory attention and language in a pattern, consistent with pre-clinical Alzheimer's disease. When controlling for ApoE allele type the odds ratio for pupil response as a risk factor increased to 4. The analysis also found that an exaggerated pupil response was a significant (p=.02) predictor of cognitive decline. This analysis of longitudinal data has shown that over time an exaggerated response on the pupil assay is a significant independent risk factor for developing pre-clinical Alzheimer's disease. The risk for developing pre-clinical Alzheimer's disease is increased four-fold.

ApoE allelic variability influences pupil response to cholinergic challenge and cognitive impairment

Exaggerated pupil response to dilute tropicamide has been suggested as an early biological marker for Alzheimer's disease. The current study links apolipoprotein E (ApoE) allelic variability to the magnitude of pupil response in a sample of community-dwelling elderly without a diagnosis of Alzheimer's disease or dementia. Possession of an epsilon 4 allele influences both the likelihood of exhibiting an exaggerated pupil response above a predetermined cut-off (13% above baseline diameter) and the absolute overall magnitude of the response. Allelic variability was also shown to correlate with cognitive impairments in memory and attention. The data in this study further elucidate the nature of the biological bond between an exaggerated pupil response and the pathology of Alzheimer's disease. ApoE allelic variability is probably linked to pupil response through its influence on tau hyperphosphorylation. The early Alzheimer's pathology seen in the Edinger-Westphal area of cranial nerve III, a major centre for pupil control, is primarily tau-based with significant cell loss in this nucleus leading to central denervation hypersensitivity even in elderly who are clinically silent but who have early pathology.

Selective cell loss in Edinger-Westphal in asymptomatic elders and Alzheimer's patients

Exaggerated pupillary response to a low concentration of cholinergic antagonists has been suggested as an early marker for Alzheimer's Disease (AD). To examine the anatomic basis of this phenomenon, we determined possible neuropathological changes in the Edinger-Westphal (EW) nucleus, a midbrain neural center with a significant functional role in the control of pupil size. Stereologically determined neuronal numbers within the EW were counted in individuals with pathologically confirmed AD, control cases with no AD-type pathology, and subjects with AD pathology not meeting diagnostic criteria for AD. The EW of AD patients displayed a marked and striking neuronal loss when compared with controls. In contrast, the number of neurons in the somatic portion of the nucleus of the third cranial nerve (NCNIII) remained intact. The EW in brains from clinically normal individuals with evidence of early AD-type pathology also displayed a significant and selective loss of neurons. The magnitude of EW neuronal loss in the latter group was smaller than that observed in AD. These findings suggest that pupillary hypersensitivity in AD may be caused by abnormalities in the EW. Neuronal loss and pathology within the EW in a subpopulation of clinically silent controls with pathologic findings consistent with early-stage AD constitutes a possible explanation for the reported exaggerated pupil response in some normal elderly subjects.

Recent advances in dementia research in Japan: Alzheimer-type dementia

In a previous article, recent reports by Japanese researchers on non-Alzheimer-type degenerative dementias were reviewed. In the present article, recent Japanese reports on Alzheimer-type dementia (ATD) are reviewed. Alzheimer-type dementia has received great attention and has been studied from various viewpoints in Japan as well as in Europe and the Americas. In Japan, although it was believed that vascular dementia was the most frequent dementia in the elderly, ATD has recently been shown to be the most predominant type of dementia. Such a great number of papers on ATD have been reported in Japan that mainly the clinical, neuropathological, biochemical and molecular biological research papers alone are reviewed here.

Altered pupillary size and darkness and light reflexes in Alzheimer's disease

The purpose was to compare resting pupil diameter in darkness and light, and the pupillary darkness and light reflexes between a group of patients with Alzheimer's disease and a group of healthy old people. Nine medication free patients with Alzheimer's disease and nine healthy control subjects, matched for sex and age with the patients, participated. There were six men and three women and the median age was 72 years in both groups. Pupil diameter was monitored with an infrared television pupillometer. Resting pupil diameter was smaller in the Alzheimer's disease group (P = 0.041, in darkness). The amplitude and the maximum dilatation velocity of the darkness reflex were smaller for the Alzheimer's disease group (maximum dilatation velocity P < 0.002). The amplitude and the 75% recovery time of the light reflex response were reduced in the Alzheimer's disease group (P < 0.002 and P = 0.034 respectively). There was no difference in the latency of the reflex response between the two groups. The reduced pupil size and diminished darkness reflex in the Alzheimer's disease group are consistent with a sympathetic deficit in the patients. The reduction in light reflex amplitude and recovery time are likely to be secondary to the grossly diminished pupil size in the patient group. The lack of any change in light reflex latency in the patients with Alzheimer's disease argues against an afferent defect. The pupillary changes in patients with Alzheimer's disease are qualitatively the same as those seen in healthy old people and are consistent with the notion of "accelerated aging" in Alzheimer's disease.

Biological markers for the clinical diagnosis of Alzheimer's disease

There is a compelling need to develop biological marker(s) to confirm a clinical diagnosis of Alzheimer's disease (AD) during life in order to unequivocally identify AD patients for emerging therapeutic interventions. This review describes recent advances in the development of diagnostic marker(s) for AD. They include polymorphism of apolipoprotein E (ApoE) and alpha 1-antichymotrypsin as well as cerebrospinal fluid (CSF) tau and CSF-amyloid beta-protein levels, skin biopsy, and pupil dilatation assay by anti-cholinergic agent. In conclusion, ApoE genotyping should not be used as a sole diagnostic test for AD, and that monitoring of CSF-tau appeared to be most promising and reliable diagnostic aid.