Repetitive Transcranial Magnetic Stimulation in Traumatic Brain Injury

BACKGROUND: A frequent and disabling impairment in persons who suffered traumatic brain injury (TBI) is left hemi-spatial neglect (LHSN). LHSN is a spatial attentive syndrome, characterized by a reduced ability to attend, perceive and consciously represent the left contra-lesional space, in the absence of a primary sensory deficit. Persons with LHSN fail to attend any stimulus coming from the left space and this can affect the ability to carry out many everyday tasks, such as walking, eating, reading and getting dressed. Those patients, as a direct consequence of the brain injury and LHSN, are also often affected by anosognosia for hemiplegia and for LHSN, which is the lack of awareness about motor and cognitive deficits. This condition hinders motor and cognitive recovery, predisposes to falls and reduces independence. Furthermore, in TBI LHSN is often associated with a mixture of attention, memory, executive function, and processing speed deficits leading to complex cognitive and behavioral pictures, which may even interfere with the administration of standard cognitive treatments for LHSN (i.e. visual scanning protocols or prism adaptation). It is also known that 1 Hz inhibitory repetitive Transcranial Magnetic Stimulation (rTMS), applied for two weeks to the posterior parietal cortex (PPC) of the unaffected hemisphere in patients with LHSN due to ischemic lesion of the right hemisphere, induces a significant improvement of visual-spatial symptoms that persists 15 days after rTMS treatment. These results can be explained considering that spatial attention deficit in LHSN due to a right middle cerebral artery territory stroke relates to abnormal activation of neural system that mediates spatial attentive operations in the healthy brain. In LHSN, a lesion of the right PPC and of the inter-hemispheric connectivity causes an imbalance in interhemispheric activity due to hyperactivity of the left hemisphere which, in turn, causes a biased attentive allocation towards ipsilesional space. As a consequence, an inhibition of this hyperactivity may have a rebalancing effect, reducing left spatial attention deficit in LHSN. Indeed, recent studies in stroke showed also the possibility of improving the efficacy of standard cognitive treatments (i.e. visual scanning) if the latter are preceded by inhibitory rTMS on the unaffected hemisphere. What is not known is whether also in LHSN due to TBI, inhibitory rTMS on the left PPC followed by a visual scanning protocol may be an effective treatment as in right hemisphere stroke, considering that in TBI the damage is often more widespread and multifocal than in the former condition.

AIMS:

• To compare the efficacy of a combined r-TMS and CCT intervention aiming at reducing cognitive symptoms of LHSN, in a sample of TBI patients with LHSN, within the context of an RCT.
• To evaluate the long- term impact of the intervention and evaluate the effect of the intervention on several clinical measures (activity of daily living, attentive and motor functions) and on psychophysiological indices

METHODS: Randomized controller trial, with blind assessments on pretest, postest and on 3 months follow-up.

POPULATION: TBI patients with clinical evidence of LHSN. INTERVENTION: Inhibitory low-frequency r-TMS on the left parietal cortex combined with a conventional cognitive treatment (visual scanning training) for 2 weeks.

CONTROL: SHAM group with a placebo r-TMS stimulation combined with visual scanning training for 2 weeks.

OUTCOMES: Multidisciplinary assessment with clinical and psychophysiological indices. The primary endpoint is a psychophysiological index based on Visual-Evoked Potentials (VEPs). In particular we will focus on the N1 component, a posterior negativity, which is altered in terms of latency and amplitude in LHSN population. In order to study effects of the r-TMS in the interhemispheric parietal pathway, we will extract indices of interhemispheric transmission time (IHTT) on the N1 latency and of spatial attention bias on N1 amplitude (VABI). The secondary outcomes will consider the impact of the intervention on other clinical measures of cognitive and motor impairment and on test of activity of daily living.

EXPECTED RESULTS: The main expected outcome of the present project will provide evidence, on a large simple of TBI patients, of the interhemispheric functionality underlying cognitive symptoms of LHSN. It will point out the specific effect of rTMS protocols on the inter-hemispheric imbalance. More in details, we expect to observe in the rTMS group a larger rebalancing effect than in the control group, as demonstrated by psychophysiological indexes, with the persistence of effects at follow-up. Additionally, we expect to observe larger improvements in cognitive and behavioral symptoms of LHSN induced by the rTMS in comparison to the control group, as demonstrated by better performances on clinical tests and batteries.

RANDOMIZATION: In order to ensure that each arm will contain an equal number of individuals, eligible subjects will be randomly assigned to one of the two groups with a blocked randomization method based on a block size of 4.

ASSESSOR AND PATIENT BLINDNESS: In order to ensure a double-blind assessment, pre-treatment assessments will be performed prior to randomization. An assessor not aware of the patient randomization group will conduct post-treatment and follow-up assessments. Also the visual scanning protocol will be administered by therapists unaware of the patient randomization and patients themselves will be instructed not to reveal any information on the brain stimulation treatment received.

CASE REPORT AND DATA MONITORING: Specific case report forms (CRF) for every test in the assessments are already available and will be used. During the treatment the responsible physician will report any adverse event in the treatment-CRF. All information and results will be promptly reported on the electronic database. A researcher will be responsible for the electronic database, data analyses and will draft the single patient record at the end of all procedures. In case of lost to follow-up, the information available up to that moment will be considered. If participant is lost at follow-up, it will be analyzed on the basis of the "intention to treat" principle. Finally, the reason for quit the study will be reported for each participant lost at follow-up.

SAMPLE SIZE: The sample size was calculated using the following formula:

https://www.dropbox.com/s/y56umrt7z93en1w/Simple%20size%20formula.docx? dl=0 The sample size resulting from the formula calculated for the VABI is 24. Consequently, the minimum sufficient sample to reach the primary aim is, assuming approximately 10% of subjects lost to follow-up, 28 subjects (14 X group) recruited over a three-year period.

DATA ANALYSES: Analysis of covariance will be performed for each measure using a mixed-model ANCOVA with a 2X3 design, where the "between" factor is represented by the randomization groups (rTMS, SHAM) and the "within" factor is the assessment time (T0, T1, T2). Data analysis will be performed using Matlab and SPSS softwares.