A Okello

Publications (3)19.39 Total impact

• Article: (11)C-PIB PET in subjective cognitive impairment.

  J Rodda, A Okello, P Edison, T Dannhauser, D J Brooks, Z Walker
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  ABSTRACT: People with Subjective Cognitive Impairment (SCI) may be at increased risk of dementia. In this study we examined amyloid load in 5 SCI subjects and 14 controls using PIB PET scanning. One SCI subject had significantly increased PIB retention in the cortical areas of interest. Larger, longitudinal studies are indicated.
  European Psychiatry 11/2009; 25(2):123-5. · 2.77 Impact Factor
• Source

  Available from: Kjell Någren

  Article: Conversion of amyloid positive and negative MCI to AD over 3 years: an 11C-PIB PET study.

  A Okello, J Koivunen, P Edison, H A Archer, F E Turkheimer, K Någren, R Bullock, Z Walker, A Kennedy, N C Fox, M N Rossor, J O Rinne, D J Brooks
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  ABSTRACT: Patients with amnestic mild cognitive impairment (MCI) represent an important clinical group as they are at increased risk of developing Alzheimer disease (AD). (11)C-PIB PET is an in vivo marker of brain amyloid load. To assess the rates of conversion of MCI to AD during a 3-year follow-up period and to compare levels of amyloid deposition between MCI converters and nonconverters. Thirty-one subjects with MCI with baseline (11)C-PIB PET, MRI, and neuropsychometry have been clinically followed up for 1 to 3 years (2.68 +/- 0.6 years). Raised cortical (11)C-PIB binding in subjects with MCI was detected with region of interest analysis and statistical parametric mapping. Seventeen of 31 (55%) subjects with MCI had increased (11)C-PIB retention at baseline and 14 of these 17 (82%) clinically converted to AD during follow-up. Only one of the 14 PIB-negative MCI cases converted to AD. Of the PIB-positive subjects with MCI, half (47%) converted to AD within 1 year of baseline PIB PET, these faster converters having higher tracer-retention values than slower converters in the anterior cingulate (p = 0.027) and frontal cortex (p = 0.031). Seven of 17 (41%) subjects with MCI with known APOE status were epsilon4 allele carriers, this genotype being associated with faster conversion rates in PIB-positive subjects with MCI (p = 0.035). PIB-positive subjects with mild cognitive impairment (MCI) are significantly more likely to convert to AD than PIB-negative patients, faster converters having higher PIB retention levels at baseline than slower converters. In vivo detection of amyloid deposition in MCI with PIB PET provides useful prognostic information.
  Neurology 08/2009; 73(10):754-60. · 8.31 Impact Factor
• Article: Microglial activation and amyloid deposition in mild cognitive impairment: a PET study.

  A Okello, P Edison, H A Archer, F E Turkheimer, J Kennedy, R Bullock, Z Walker, A Kennedy, N Fox, M Rossor, D J Brooks
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  ABSTRACT: Activated microglia may play a role in the pathogenesis of Alzheimer disease (AD) as they cluster around beta-amyloid (Abeta) plaques. They are, therefore, a potential therapeutic target in both AD and its prodrome amnestic mild cognitive impairment (MCI). To characterize in vivo with (11)C-(R)-PK11195 and (11)C-PIB PET the distribution of microglial activation and amyloid deposition in patients with amnestic MCI. Fourteen subjects with MCI had (11)C-(R)-PK11195 and (11)C-PIB PET with psychometric tests. Seven out of 14 (50%) patients with MCI had increased cortical (11)C-PIB retention (p < 0.001) while 5 out of 13 (38%) subjects with MCI showed increased (11)C-(R)-PK11195 uptake. The MCI subgroup with increased (11)C-PIB retention also showed increased cortical (11)C-(R)-PK11195 binding (p < 0.036) though this increase only remained significant in frontal cortex after a correction for multiple comparisons. There was no correlation between regional levels of (11)C-(R)-PK11195 and (11)C-PIB binding in individual patients with MCI: only three of the five MCI cases with increased (11)C-(R)-PK11195 binding had increased levels of (11)C-PIB retention. Our findings indicate that, while amyloid deposition and microglial activation can be detected in vivo in around 50% of patients with mild cognitive impairment (MCI), these pathologies can occur independently. The detection of microglial activation in patients with MCI suggests that anti-inflammatory therapies may be relevant to the prevention of AD.
  Neurology 01/2009; 72(1):56-62. · 8.31 Impact Factor