Myelomeningocele is a severe type of spina bifida, resulting from improper closure of the neural tube. This condition drastically affects the structures of the spinal cord, as a result the spinal cord, nerve roots and meninges are exposed during pregnancy resulting in deficiencies. The combination of these deficiencies results in an overall decrease in mobility and functional participation. There is little evidence about physical therapy interventions in this population. However, it is known that the International Classification of Functionality, Disability and Health for Children and Youth is a useful tool to assist therapists in analyzing problems and thinking about the focus of the intervention. The current literature demonstrates that resources such as low intensity light, also known as photobiomodulation as a therapeutic means, can be auxiliary means in the rehabilitation of neurological conditions, as studies show that photobiomoduction promotes sensory and motor recovery in the animal model of spinal cord injury . And a clinical trial showed that after photobiomodulation treatment combined with photobiomodulation, individuals with spinal cord injuries improved motor and sensory function. Therefore, the objective of the study is to evaluate the effects of physical therapy associated with photobiomodulation on functional performance in children with low and sacral lumbar myelomeningocele. Materials and methods: Participants will be recruited at the Integrated Health Clinic of University Nove de Julho. Those who meet the inclusion criteria will be randomized to two groups using a randomization site (randomization.com). Group 1 will be submitted to active PBM and physiotherapeutic exercises. Group 2 will be submitted to sham PBM and physiotherapeutic exercises. Irradiation will be carried out with LED at a wavelength of 850 nm, energy of 25 J per point, 50 seconds per point and a power of 200 mW. The same device will be used in the placebo group but will not emit light. Muscle activity will be assessed using a portable electromyograph (BTS Engineering) and the sit-to-stand task will be performed as a measure of functioning. Electrodes will be positioned on the lateral gastrocnemius, tibialis anterior and rectus femoris muscles. The Pediatric Evaluation of Disability Inventory will be used to assess the functional independence of the children. Quality of life will be assessed using the Child Health Questionnaire - Parent Form 50. Change in participation will be assessed using the Participation and Environment Measure for Children and Youth (PEM-CY). The sensory evaluation will be performed using the Semmes-Weinstein kit (AesthesioVR kit, California, EUA, DanMic Global). The protein expression of BDNF will be quantified from saliva samples using the ELISA technique. The data will be analyzed with the aid of GraphPad PRISM. The results of this study can contribute to a better understanding of the effectiveness of physiotherapy on the functionality and quality of life of children with myelomeningocele. In addition, FBM is a non-invasive treatment, and a fast procedure and can be a promising approach in the treatment

Inclusion Criteria:

• diagnosis of myelomeningocele on the lower lumbar and sacral level;
• able to perform the movement of sitting and standing with support

Exclusion Criteria:

• Cognitive impairment that compromises the ability to communicate
• Allergy to latex; neuromuscular scoliosis; subluxation or dislocation of the hip and knee;
• other disease of the central nervous system.

• Participants will not know whether which group they are participating in, that is, treatment group or placebo with photobiomodulation.
• The evaluator and who will perform the exercises will not know which group the participant is participating in relation to photobiomodulation.
• A therapist who will not participate in assessments and physiotherapy sessions will perform the application of photobiomodulation.
• The microtubes with the saliva samples will be marked with numbers corresponding to each participant, so the evaluator will not know which group the sample corresponds to. A therapist will be responsible for the assessment and electromyography scales.