Keywords:
Neuroradiology brain, MR-Functional imaging, Diagnostic procedure, Seizure disorders
Authors:
V. Sawlani, K. Kawsar, D. McCorry, A. Hawkins, J. Herbert, R. Chelvarajah; Birmingham/UK
DOI:
10.26044/ecr2019/C-1993
Methods and materials
Method
From July 2014 to April 2017,
26 memory fMRI was done on epileptic patients who are deemed suitable for temporal lobe resection surgery.
No WADA test was performed.
FMRI was performed on 3T Siemens Vario MRI scanner.
Sequence Parameters were: EPI sequence with TR 3000ms,
TE 30ms,
in-plane resolution 3.9mm (64x64 matrix,
FOV 250 mm),
slice thickness 3mm (gap 25%).
Home-town walk memory paradigm consisted of 10 sets of Active-Baseline blocks.
Fig. 1: A stimulus is repeatedly presented for a block period of time (30 sec), followed by a period of ‘rest’ in which the haemodynamic response is allowed to return to a resting baseline. Brain activity is averaged across all trials within the block.
The fMRI is performed on two consecutive days with a block design using same paradigm.
The task requires mental navigation through one's hometown by using landmarks given by patients themselves (Roland’s Hometown walking task).
Fig. 2: Example of an imaginary walk
Hometown Walking Paradigm
The Hometown walking paradigm reflects a number of things:3,4
- The greater complexity of the hometown-walking task produced stronger activations
- Activation of parahippocampal and fusiform gyri,
with little activation in the hippocampus
- Activation in the posterior cingulate is related to visuospatial memory processes
- Activation in the parietal cortex related to mental navigations and imagination
- Activation of the dorsolateral prefrontal cortex probably reflecting the need for sequencing and planning
Neuropsychometric assessment
All the patients worked up for temporal lobe surgery undergo neuropsychometric assessment including memory functions before and Twelve months after the surgery.
This includes:
- Intellectual Functions: Two subtests from the Wechsler Adult Intelligence Scale
- Memory Functions: Subtests from the Wechsler Memory Scale.
Auditory Memory Index (AMI) and Visual Memory Index (VMI)
- Attention & Executive Functions: (WAIS-IV PSI).
Verbal Fluency and Colour-Word Interference)
- Language Functions: Boston Naming Test – Second Edition (BNT-2)