Repetitive Transcranial Magnetic Stimulation for Post-Stroke Visual Field Defects
Condition: Visual Fields Hemianopsia; Stroke, Ischemic; Stroke Hemorrhagic
MeSH terms: Stroke; Ischemic Stroke; Hemorrhagic Stroke; Hemianopsia
Study type: Interventional

Summary: 
      Visual field defects (VFD) usually do not show improvement beyond 12 weeks from onset.
      Plasticity occurs in areas of residual vision (ARV) at the visual field which are the
      functional counterpart of partially damaged brain regions at the areas around brain lesion.
      Few treatment options are currently available for post-stroke VFD. In this pilot study, the
      effect of repetitive transcranial magnetic stimulation (rTMS) applied to these areas on VFD
      in patients with cortical infarction will be studied. Patients will be divided into two
      groups; an active group which will receive active stimulation and a sham group which will
      receive placebo stimulation through a sham coil.
    

Detailed 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.
    

Intervention name(s): High frequency repetitive transcranial magnetic stimulation (rTMS); Sham stimulation
Intervention type(s): Device; Device
Intervention description(s): 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.; 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.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Double (Participant, Outcomes Assessor)
Primary purpose: Treatment
Keywords: Transcranial Magnetic Stimulation