A prospective cross-sectional study was conducted at the Diagnostic Radiology Department. It was performed in the period from May 2017 to May 2019.
A total of 16 Alzheimer patients (9 males and 7 females) were recruited, ranging from 63 to 86 years of age, with a mean education level of 3.94 ± 1.24 years. Patients with AD were included after clinical neurological evaluation (according to the criteria of the National Institute of Neurological and Communicative Disorders and Stroke Alzheimer Disease and Related Disorders Association) .
In addition, 16 control subjects (9 males and 7 females), with normal memory and cognition with no history of neurological or psychiatric disorders, were included. Control subjects were matched with AD patients for age and education level, age range from 58 to 80 years, with a mean education level of 5.06 ± 1.24 years.
All participants or their caregivers gave informed consent before participation in the investigation and after the full explanation of the study protocol. The study was approved by the local ethical committee.
Exclusion criteria included patients with other types of dementia such as fronto-temporal dementia or any other factors causing dementia and patients with pyramidal or extrapyramidal tract signs. Any patient with moderate or profound subcortical ischemic changes, structural abnormalities in the brain and/or any metallic prosthesis was excluded.
For staging of dementia, patients were classified into mild, moderate, and severe AD according to Modified Mini-Mental State Examination (MMMSE) and Clinical Dementia Rating (CDR).
Each patient was evaluated with MMMSE by a trained neuropsychologist. It is a measure of global cognition, for assessing orientation, attention, language, and memory. The cutoff point ≤23 is used in order to detect suspected demented subjects. Dementia was classified according to the MMMSE score as 23–19, 18–11, and less than 11 for mild, moderate, and severe dementia, respectively, using the full score of 30 points in the case of educated patients .
The CDR is a numeric scale used to quantify the severity of symptoms of dementia. A structured interview protocol for the assessment of a patient’s cognitive and functional performance in six areas was used: memory, orientation, judgment and problem solving, community affairs, home and hobbies, and personal care.
MRI examination was performed at a 1.5-T unit (Achieva, Phillips Healthcare) using the standard head coil for signal perception.
3D fluid-attenuated inversion recovery (FLAIR) images were acquired with FLAIR sequences (TR/TE = 11,000/140ms, matrix= 208×106, voxel size 1 × 1 × 1mm). DTI was obtained using an echo-planner imaging sequence with a b value of 1000 s/mm2 and a b value of 0s/mm2, 32 uniform directions, and a matrix size of 112 × 112 with a 2-mm isotropic spatial resolution. TR/TE is equal to 11,785/110 ms. The slice thickness was 2 mm. The examination time of this sequence was 13.33 min.
After data preparation, images were transferred to the Philips Workstation software package; the 2 maps were obtained (FA and MD colored maps). Processing was performed on colored FA maps where 3D FLAIR was overlaid.
The color maps provide information about the orientation of the tracts, where red color indicates a latero-lateral direction (left to right and right to left), green color an anterior-posterior direction (and vice versa), and blue color a dorsal-ventral direction (and vice versa). Other colors indicate intermediate orientations.
The following WM tracts were manually dissected using either single or two ROI (region of interest) approaches. Single ROI approach was used for the fornixes, anterior thalamic radiation (ATR), cingulum, and corpus callosum (genu, body, and splenium) . Two ROI approaches were drawn for arcuate fasciculus (AF), uncinate fasiculus (UF), inferior longitudinal fasiculus (ILF), and inferior occipito-frontal fasciculus (IFOF) bilaterally [15, 16]. The tracts were dissected conjointly by two radiologists: a resident (SMA) with 4 years of experience and a consultant radiologist (RKS) with over 10 years of experience.
Data was collected and analyzed using SPSS (Statistical Package for the Social Science, version 20, IBM, and Armonk, NY). Continuous data was expressed in the form of mean ± SD while nominal data was expressed in the form of frequency (percentage).
The chi-squared test was used to compare the nominal data of different groups in the study while the Student t test was used to compare the mean of DTI parameters (FA and MD) of the selected WM tracts between AD patients and control subjects. The diagnostic performance of significant DTI parameters was determined by the ROC curve. The level of confidence was kept at 95%; hence, P value was significant if < 0.05.