Repetitive Transcranial Magnetic Stimulation for Post-Stroke Visual Field Defects
Keywords
Abstract
Description
Visual functions are widely distributed over large areas within the cerebrum. Secondary to such wide distribution, visual field defects (VFD) are a common outcome of brain insults especially cerebrovascular stroke whether hemorrhagic or ischemic. Among these, homonymous hemianopia is the most frequently encountered VFD in clinical practice. VFD ranges from 8.3% to 16% in the chronic stage of stroke, while it reaches 25% in acute and subacute stages of stroke. In other studies, it was reported to be even higher. In a database of 11900 stoke patients, VFD was found in 60.5% with homonymous hemianopia accounting for 35%.
These VFDs usually show some degree of improvement within few months from onset secondary to resolution of edema and diaschisis, yet by 3 to 6 months the condition tends to become stationary with no further improvement and only 5% of patients will show full recovery of their visual field. In some studies recovery was mostly along the first 10 days of insult followed by decrease in recovery rate that nearly stops 10-12 weeks after insult. Beyond this time point, very few cases develop spontaneous recovery.
Plasticity occurs in areas of residual vision (ARV) at the visual field borders rather than areas of absolute blindness. These ARVs are the functional counterpart of partially damaged brain regions at the perilesional areas. Recovery of function - both early in life and in adults - is stimulation dependent. This stimulation can be either through visual experience, behavioral training or brain stimulation. To the investigator's knowledge, direct current stimulation (DCS) is the only brain stimulation modality that has been studied in cases of VFDs. Results showed that DCS can expand visual field in stroke patients with the effects being stable over time.
In the current study, it is hypothesized that stimulation of the perilesional seemingly healthy brain tissue close to the visual cortex would result in clinical improvement based on the concept of ARVs. To achieve this precise targeting, navigated rTMS would be the most suitable technique.
The investigators aim to study the effect of navigated repetitive transcranial magnetic stimulation (rTMS) applied to perilesional areas on patients with cortical visual field defects (cVFD) due to stroke.
This is a randomized sham-controlled clinical trial that will be conducted in the neuromodulation research lab, neurology department, Ain Shams University. The study is approved by Ain Shams University faculty of medicine local research ethics committee (REC).
Procedures:
3D MRI: An MRI Brain T1WI with 200 cuts of 0.9 mm sections will be obtained. Segmentation of the head model will be done to separate scalp, skull and brain layers. A three-dimensional virtual head model will then be created for each patient.
Target Selection: The target for stimulation will be determined and marked for each patient using a neuronavigation system on his virtual head model. Targets will be selected along the perilesional area in the nearest seemingly healthy tissue to the visual cortex based on the following steps:
1. ARV (grey zone) will be identified in the perimetry of the patient.
2. Corresponding area in the 3D head model will then be determined based on visuotopy of the primary visual cortex.
Dates
| Last Verified: | 06/30/2019 |
| First Submitted: | 04/05/2019 |
| Estimated Enrollment Submitted: | 07/12/2019 |
| First Posted: | 07/15/2019 |
| Last Update Submitted: | 07/12/2019 |
| Last Update Posted: | 07/15/2019 |
| Actual Study Start Date: | 05/31/2018 |
| Estimated Primary Completion Date: | 09/30/2019 |
| Estimated Study Completion Date: | 10/31/2019 |
Condition or disease
Intervention/treatment
Device: Active Group
Device: Sham Group
Phase
Arm Groups
| Arm | Intervention/treatment |
|---|---|
| Active Comparator: Active Group A total of 16, every other day sessions of rTMS at 10 Hz frequency will be applied to 4 locations along the perilesional area (see target selection). Intensity will be 100% of motor threshold, 25 trains - 40 pulses per train with 20 seconds intertrain interval and a total of 1000 pulses per session. The coil handle will be directed downwards at 45º of the sagittal plain to ensure that the induced electric field be perpendicular to the underlying gyrus. | Device: Active Group 10hz, 20 seconds intertrain interval, 40 pulses per train with a total of 1000 pulse per session given at 100% of motor threshold. A total of 16 sessions will be given to each patient. |
| Sham Comparator: Sham Group Sham group will receive the same sessions as above with the exact same parameters yet a sham coil identical in shape and size to the active coil will be used instead. The sham coil produces sounds and sensations very similar to the active one. | Device: Sham Group A sham coil will be used that is shielded so that it produces sounds and sensations similar to the active coil but does not produce therapeutic effects. 10hz, 20 seconds intertrain interval, 40 pulses per train with a total of 1000 pulse per session given at 100% of motor threshold. A total of 16 sessions will be given to each patient. |
Eligibility Criteria
| Ages Eligible for Study | 18 Years To 18 Years |
| Sexes Eligible for Study | All |
| Accepts Healthy Volunteers | Yes |
| Criteria | Inclusion Criteria: - Patients with a brain imaging showing vascular lesion involving visual cortical area - Duration of at least 3 months. Exclusion Criteria: - Visual field defects of ophthalmologic origin - Causes of severe visual impairment other than visual field defects - Drug abuse - Past history or family history of epilepsy - Skull bone defects - Implanted metallic devices |
Outcome
Primary Outcome Measures
1. Change in Mean Deviation (MD) of Automated Perimetry [6 weeks]
Secondary Outcome Measures
1. Change in Visual Field Index (VFI) of Automated Perimetry [6 weeks]
2. National Eye Institute Visual Functioning Questionnaire-25 (VFQ-25) [6 weeks]
