Automated and manual hippocampal segmentation techniques: Comparison of results, reproducibility and clinical applicability.

BACKGROUND: Imaging techniques used to measure hippocampal atrophy are key to understanding the clinical progression of Alzheimer's disease (AD). Various semi-automated hippocampal segmentation techniques are available and require human expert input to learn how to accurately segment new data. Our goal was to compare 1) the performance of our automated hippocampal segmentation technique relative to manual segmentations, and 2) the performance of our automated technique when provided with a training set from two different raters. We also explored the ability of hippocampal volumes obtained using manual and automated hippocampal segmentations to predict conversion from MCI to AD. METHODS: We analyzed 161 1.5 T T1-weighted brain magnetic resonance images (MRI) from the ADCS Donepezil/Vitamin E clinical study. All subjects carried a diagnosis of mild cognitive impairment (MCI). Three different segmentation outputs (one produced by manual tracing and two produced by a semi-automated algorithm trained with training sets developed by two raters) were compared using single measure intraclass correlation statistics (smICC). The radial distance method was used to assess each segmentation technique's ability to detect hippocampal atrophy in 3D. We then compared how well each segmentation method detected baseline hippocampal differences between MCI subjects who remained stable (MCInc) and those who converted to AD (MCIc) during the trial. Our statistical maps were corrected for multiple comparisons using permutation-based statistics with a threshold of p < .01. RESULTS: Our smICC analyses showed significant agreement between the manual and automated hippocampal segmentations from rater 1 [right smICC = 0.78 (95%CI 0.72-0.84); left smICC = 0.79 (95%CI 0.72-0.85)], the manual segmentations from rater 1 versus the automated segmentations from rater 2 [right smICC = 0.78 (95%CI 0.7-0.84); left smICC = 0.78 (95%CI 0.71-0.84)], and the automated segmentations of rater 1 versus rater 2 [right smICC = 0.97 (95%CI 0.96-0.98); left smICC = 0.97 (95%CI 0.96-0.98)]. All three segmentation methods detected significant CA1 and subicular atrophy in MCIc compared to MCInc at baseline (manual: right pcorrected = 0.0112, left pcorrected = 0.0006; automated rater 1: right pcorrected = 0.0318, left pcorrected = 0.0302; automated rater 2: right pcorrected = 0.0029, left pcorrected = 0.0166). CONCLUSIONS: The hippocampal volumes obtained with a fast semi-automated segmentation method were highly comparable to the ones obtained with the labor-intensive manual segmentation method. The AdaBoost automated hippocampal segmentation technique is highly reliable allowing the efficient analysis of large data sets.

Cerebrospinal fluid Aß levels correlate with structural brain changes in Parkinson's disease.

ParkWest is a large Norwegian multicenter study of newly diagnosed drug-naïve subjects with Parkinson's disease (PD). Cognitively normal PD subjects (PDCN) and PD subjects with mild cognitive impairment (PDMCI) from this cohort have significant hippocampal atrophy and ventricular enlargement, compared to normal controls. Here, we aimed to investigate whether the same structural changes are associated with cerebrospinal fluid (CSF) levels of amyloid beta (Aß)38 , Aß40 , Aß42 , total tau (t-tau), and phosphorylated tau (p-tau). We performed three-dimensional radial distance analyses of the hippocampi and lateral ventricles using the MRI data from ParkWest subjects who provided CSF at baseline. Our sample consisted of 73 PDCN and 18 PDMCI subjects. We found significant associations between levels of all three CSF Aß analytes and t-tau and lateral ventricular enlargement in the pooled sample. In the PDCN sample, all three amyloid analytes showed significant associations with the radial distance of the occipital and frontal horns of the lateral ventricles. CSF Aß38 and Aß42 showed negative associations, with enlargement in occipital and frontal horns of the lateral ventricles in the pooled sample, and a negative association with the occipital horns in PDMCI. CSF Aß levels in early PD correlate with ventricular enlargement, previously associated with PD dementia. Therefore, CSF and MRI markers may help identify PD patients at high risk for developing cognitive decline and dementia in the course of their illness. Contrary to Alzheimer's disease, we found no associations between CSF t-tau and p-tau and hippocampal atrophy.

Verbal memory is associated with structural hippocampal changes in newly diagnosed Parkinson's disease.

BACKGROUND AND OBJECTIVE: Cognitive impairment, including impairment of episodic memory, is frequently found in newly diagnosed Parkinson's disease (PD). In this longitudinal observational study we investigated whether performance in memory encoding, retention, recognition and free recall is associated with reduced hippocampal radial distance. METHODS: We analysed baseline T1-weighted brain MRI data from 114 PD subjects without cognitive impairment, 29 PD subjects with mild cognitive impairment and 99 normal controls from the ParkWest study. Age- and education-predicted scores for the California Verbal Learning Test 2 (CVLT-2) and tests of executive function were regressed against hippocampal radial distance while adjusting for imaging centre. RESULTS: There was no association between encoding or performance on executive tests and hippocampal atrophy in the PD group. In the full PD sample we found bilaterally significant associations between lower delayed free recall scores and hippocampal atrophy in the CA1, CA3 and subiculum area (left, p=0.0013; right, p=0.0082). CVLT-2 short delay free recall scores were associated with bilateral hippocampal CA1 and subicular atrophy in the full PD sample (left, p=0.013; right, p=0.047). CVLT-2 recognition scores showed a significant association with right-sided subicular and CA1 atrophy in the full PD sample (p=0.043). CONCLUSIONS: At the time of PD diagnosis, subjects' verbal memory performance in recall and recognition are associated with atrophy of the hippocampus, while encoding is not associated with hippocampal radial distance. We postulate that impaired recall and recognition might reflect deficient memory consolidation at least partly due to structural hippocampal changes.

Comparing hippocampal atrophy in Alzheimer's dementia and dementia with lewy bodies.

BACKGROUND/AIMS: Dementia with Lewy bodies (DLB) and Alzheimer's disease (AD) are the two most common neurodegenerative dementias. During the early stages, clinical distinction between them is often challenging. Our objective is to compare hippocampal atrophy patterns in mild AD and mild DLB. We hypothesized that DLB subjects have milder hippocampal atrophy relative to AD subjects. METHODS: We analyzed the T1-weighted magnetic resonance imaging data from 113 subjects: 55 AD, 16 DLB and 42 cognitively normal elderly (normal controls, NC). Using the hippocampal radial distance technique and multiple linear regression, we analyzed the effect of clinical diagnosis on hippocampal radial distance, while adjusting for gender and age. Three-dimensional statistical maps were adjusted for multiple comparisons using permutation-based statistics with a threshold of p < 0.01. RESULTS: Compared to NC, AD exhibited significantly greater atrophy in the cornu ammonis (CA)1, CA2-3 and subicular regions bilaterally while DLB showed left-predominant atrophy in the CA1 region and subiculum. Compared directly, AD and DLB did not reveal statistically significant differences. CONCLUSION: Hippocampal atrophy, while present in mildly impaired DLB subjects, is less severe than atrophy seen in mildly impaired AD subjects, when compared to NC. Both groups show predominant atrophy of the CA1 subfield and subiculum.

SCOPA-AUT scale in different parkinsonisms and its correlation with (123) I-MIBG cardiac scintigraphy.

INTRODUCTION: Our objective was to assess the usefulness of the Scales for Outcomes in Parkinson's disease - Autonomic (SCOPA-AUT) in the differential diagnosis of Parkinsonisms and clarify its relation with 123-I-MIBG cardiac scintigraphy. METHODS: A total of 112 patients with Parkinson's disease (PD), 12 with multiple system atrophy parkinsonian variant (MSA-P) and 20 with progressive supranuclear palsy (PSP) participated in the study. The following variables were collected: age, sex, age at onset, length of illness, type and dose of anti-Parkinson medication, and score on the Unified Parkinson's Disease Rating Scale. The Unified Multiple System Atrophy Rating Scale was administered to patients with MSA and the Progressive Supranuclear Palsy Rating Scale to those with PSP. Finally, the SCOPA-AUT was administered to all the patients. Cardiac 123I-MIBG SPECT scans were performed on a subset of patients (25 with PD and 5 with MSA-P). RESULTS: Statistically significant differences were observed (p < 0.01) in the SCOPA-AUT scores between patients with PD (14.75+/-8.09) and those with MSA (21.07+/-5.56), the latter having higher scores on the bowel function (20.07+/-13.40 vs 34.92+/-14.91) and urinary domains (30.21+/-21.55 vs 49.26+/-21.40) (p < 0.01). No correlation was found between the SCOPA-AUT score and anti-Parkinson's medication and heart:mediastinum (H/M) MIBG uptake ratio in the cardiac SPECT (at 4 h). DISCUSSION: Severity of dysautonomia as measured by the SCOPA-AUT was not correlated with clinical severity, time since onset or the H/M ratio. In the patients with PD, the only variable associated with the H/M ratio was age at onset of the disease.

Initial neuropsychological impairments in patients with the E46K mutation of the α-synuclein gene (PARK 1).

INTRODUCTION: In 2004 we described the mutation E46K of the α-Synuclein (SNCA). These patients show Parkinson's disease with early cognitive impairment, sleep disorders and autonomic dysfunction. OBJECTIVE: The main objective is to identify early neuropsychological impairments in patients with the E46K mutation. METHODS: This is a longitudinal neuropsychological study of 4 of the 5 surviving patients with E46K mutation by semi-structured interviews and the following scales: Mattis Dementia Rating Scale (MDRS), semantic and phonemic verbal fluency tests (VFT), Benton Visual Retention Test (BVRT), Stroop Test (STROOP), Clock drawing test (CLOCK), WAIS III Letter and Number sequencing (WAIS III LN), Rey Auditory Verbal Learning Test (RAVLT) and Benton Judgement of Line Orientation Test (BJLOT). Motor status was assessed by UPDRS III. RESULTS: Motor status: Patients 1, 2 and 3 present mild to moderate Parkinson disease of 7, 8 and 3years of evolution respectively, patient 4 is asymptomatic. Cognitive status: Patient 2 and 3 both refer cognitive decline while patient 1 presents no cognitive complaints, however they all show a progressive cognitive decline across various tasks. Tests of frontal function showed the first alterations in all patients but fluctuate. The first cognitive complaints coincide with deterioration of tasks of posterior cortical basis. Patient 4 presents a normal performance on all tests. Patient 1, 2 and 3 have all presented visual hallucinations. CONCLUSIONS: A fluctuating frontal impairment is observed at early stages. Prominent visuospatial alterations and visual hallucinations suggest that posterior cortical dysfunction might be a distinct early feature of the cognitive impairment observed in patients with this mutation.