Multi-Modal Sensory Stimulation
26th July 2019
Aren’t we all able to attend better when we learn through more than one sensory medium? Read it, listen to it, visualize it, and write it.
That is the underlying principle behind Multi-Modal Sensory Stimulation (MMSS) - creating a sensory rich environment for patients with Disorders of Consciousness (DoC) to promote their arousal, alertness and behavioural responses.
What is MMSS?
Sensory stimulation is a collective of approaches that involves presenting simple, structured, frequent and repetitive stimuli that could elicit a behavioural response from the patient. The stimulus is considered more efficient when it is autobiographical (that the patient can relate to) and has an emotional quotient. When 2 or more sensory systems (vision, hearing, proprioception, smell and taste) are targeted simultaneously it’s referred to as multimodal stimulation. The stimulation of multiple primitive sensory modalities is said to be most effective as these signals bypass the thalamus and directly activate the hippocampus region and the limbic system in the brain. It helps to present contrasting, i.e., giving pleasant/comforting/ soft stimulus followed by an aversive/ uncomfortable stimulus within each modality such that it can elicit differentiated responses from the patients, and also help increase their alertness.
Who do we do it for?
Multimodal sensory stimulation is said to target the arousal and behavioural responsiveness, thus making people with Disorders of Consciousness (DoC) excellent candidates. People who survived Traumatic Brain Injuries (TBI) often go through a period of complete unconsciousness or coma with no awareness of themselves and those around. This state of unconsciousness and poor state of arousal is termed as DoC. Recent studies have shown a possible residual cognitive functioning of DOC patients, that is, they are able to produce some covert responses (such as hand movements) when given complex, meaningful sensory stimulation.
Why Multi-modal? What does the literature say?
MMSS has been reported to be more successful in eliciting responses in comparison to unimodal presentation (i.e., presenting stimulus through only one sensory mode). When we target multiple sensory channels, with moderate to high intensity presentation, it taps into ‘islands of high- order cognitive functioning’ which has been reported to be preserved in most patients with DoC. Thus, presenting high intensity stimuli through multiple channels (for instance, giving auditory instructions while giving ice- touch on the hand), in comparison to simple, meaningless stimulations, might evoke a response due to their intact complex cognitive skills (Lancioni et al, 2011). Unimodal stimulation does not capture attentional sources in the brain.
Also, sensory stimulation being a low invasive, not- dangerous, simple to apply and inexpensive method of treatment, it’s attractive and sought after by rehabilitation teams.
What are the sensory domains targeted?
Multimodal stimulation requires that two or more sensory domains are simultaneously stimulated, in any preferred combination. The sensory domains include:
- Visual Stimulation
- Auditory Stimulation
- Tactile Stimulation
- Olfactory Stimulation
- Gustatory Stimulation
- Vestibular Stimulation
- Kinaesthetic Stimulation
- Proprioceptive Stimulation
The Occupational Therapist and/ or the Speech and Language Pathologist carries out the stimulation program at the rehabilitation unit. They work alongside the physician, social worker and family members/caretakers to devise the stimulation plan along with a personalized material kit. After drawing a baseline assessment of the existing cognitive and sensory skills, an individualized stimulation plan is constructed based on their strongest sensory system and least responsive sensory system. The material kit consists of all the items required to carry forward the sensory stimulation program ranging from tactile stimulation materials such as cotton to oral sensory items such as honey. The program can span from 4 weeks to 6 months depending on the prognosis of the patient and the time lapse since injury and commencement of intervention.