Hyperexcitability of brain stem pathways in cerebral palsy

Abstract

Individuals with cerebral palsy (CP) experience impairments in the control of head and neck movements, suggesting dysfunction in brain stem circuitry. To examine if brain stem circuitry is altered in CP, we compared reflexes evoked in the sternocleidomastoid (SCM) muscle by trigeminal nerve stimulation in adults with CP and in age/sex-matched controls. Increasing the intensity of trigeminal nerve stimulation produced progressive increases in the long-latency suppression of ongoing SCM electromyography in controls. In contrast, participants with CP showed progressively increased facilitation around the same reflex window, suggesting heightened excitability of brain stem pathways. We also examined if there was altered activation of cortico-brain stem pathways in response to prenatal injury of the brain. Motor-evoked potentials (MEPs) in the SCM that were conditioned by a prior trigeminal afferent stimulation were more facilitated in CP compared with controls, especially in ipsilateral MEPs that are likely mediated by corticoreticulospinal pathways. In some participants with CP, but not in controls, a combined trigeminal nerve and cortical stimulation near threshold intensities produced large, long-lasting responses in both the SCM and biceps brachii muscles. We propose that the enhanced excitatory responses evoked from trigeminal and cortical inputs in CP are produced by heightened excitability of brain stem circuits, resulting in the augmented activation of reticulospinal pathways. Enhanced activation of reticulospinal pathways in response to early injury of the corticospinal tract may provide a compensated activation of the spinal cord or, alternatively, contribute to impairments in the precise control of head and neck functions. NEW & NOTEWORTHY This is the first study to show that in adults with spastic cerebral palsy, activation of brain stem circuits by cortical and/or trigeminal afferents produces excitatory responses in anterior neck muscles compared with inhibitory responses in age/sex-matched controls. This may reflect a more excitable reticulospinal tract in response to early brain injury to provide a compensated activation of postural muscles. On the other hand, a hyperexcitable brain stem may contribute to impairments in the precise control of head and neck functions.

Transcutaneous Spinal Neuromodulation Reorganizes Neural Networks in Patients with Cerebral Palsy

“…It is generally assumed that the primary pathology of the nervous system that leads to CP is located within and among different combinations of supraspinal networks, and these pathologies can be due to multiple etiologies. In most cases, however, it appears that these supraspinal pathologies also will be necessarily manifested as spinally mediated dysfunctions, affecting multiple peripheral sensory-motor systems including midline orientation, equilibrium, posture (including trunk and head control), locomotion, and trunk and head control [6]. Also, the visual system often is impacted in children with CP, because normally, the brain and spinal networks provide a key, coherent driving factor to accommodate a 1G environment in controlling posture.…”

Intraoperative Monitoring of Scoliosis Surgery in Young Patients

“…95 This is consistent with our experience; indeed MEPs are often quite robust in patients with CP, perhaps reflecting motor system hyperexcitability. 96 Although common in patients with CP, coexistence of a seizure disorder does not preclude MEP monitoring, perhaps related to the protective effects of anesthesia. 52,97…”

Technical Aspects of Eliciting Trigeminocervical and Trigeminospinal Reflexes in Humans: A Scoping Review

“…Trigeminocervical reflex and TSR were assessed by stimulation of the supraorbital nerve in 17 studies, 1,3,5,11,12,18,21,26,31,34,[36][37][38][39][41][42][43] infraorbital nerve in 14 studies, 1,2,4,5,9,10,[15][16][17]19,20,22,25,36 mental nerve in four studies, 5,32,33,36 and masseteric nerve in one study. 40 Stimulation parameters, feasibility in healthy participants, and topographic distribution of long-latency TCR and TSR recordings with electrical single-pulse stimulation of the supraorbital, infraorbital, and mental nerves are summarized in Table 2. The type of stimulation and registration electrodes, filter setting, analysis time, and gain or sensitivity are summarized in Supplemental Digital Content 6 (see Table S5, http://links.…”