Neonatal-Onset Brainstem Reticular Reflex Myoclonus Following a Prenatal Brain Insult: Generalized Myoclonic Jerk and a Brainstem Lesion

Abstract

Brainstem reticular reflex myoclonus (BRRM) is characterized by sudden, generalized, shock-like movements that can be elicited by sensory stimulation. We present a boy, born after 35 weeks gestation, who was diagnosed with neonatal-onset BRRM. Within 1 hr of birth, the patient showed spasticity and generalized clonic movements of all limbs elicited with tactile stimulation anywhere on the body. Surface electromyography showed co-contraction of agonistic and antagonistic muscles, revealing that his generalized clonic movements were tremulous myoclonus in nature. Brain magnetic resonance imaging (MRI) at 21 hrs after birth disclosed highintensity lesions in the Rolandic area, thalamus, basal ganglia, and brainstem, including the dorsal pons and medulla, the center of BRRM, in T1-weighted images. Follow-up MRI at 1 month revealed dramatic improvement in the pontine lesion. The patient showed gradual remission of the characteristic movements, which disappeared at 1 year of age, but the patient died unexpectedly at 1 year and 3 months. In conclusion, neonatal BRRM arises as a result of severe brainstem injury, and the associated lesions may only be seen temporarily on MRI taken soon after birth. prenatal brain insult; brainstem lesion; brainstem reticular reflex myoclonus; stimulus-sensitive generalized clonic movement

Post-hypoxic Myoclonus: Current Concepts, Neurophysiology, and Treatment

“…25 A single report with EMG mentioned co-contraction between muscles but no recruitment order or duration was given. 26 Without more documented surface EMG studies of the generalized jerk, it is difficult to assign an exact relationship between the EEG discharges and the jerk as well as to define the myoclonus source in general. The exact neuronal damage and pathophysiology that gives origin to acute PHM is not clear.…”

“…27 It is possible that acute PHM can arise from the cortex or a subcortical structure. 26 Indeed, it is hard to determine the origin of myoclonus on the basis of clinical judgment since multiple pathophysiology mechanisms may produce similar clinical phenomena. 12 Hallett et al in 1977 28 described the origin of myoclonus after posthypoxic injury in the reticular formation of the medulla oblongata and called this ''reticular reflex myoclonus.''…”

Post-hypoxic Myoclonus: Current Concepts, Neurophysiology, and Treatment

“… Patient did not regain consciousness and died. Kakisaka et al 26 EEG: burst suppression pattern.EMG: agonist and antagonist muscle contract simultaneously. Patient survived with significant disabilities.…”

“… 25 A single report with EMG mentioned co-contraction between muscles but no recruitment order or duration was given. 26 Without more documented surface EMG studies of the generalized jerk, it is difficult to assign an exact relationship between the EEG discharges and the jerk as well as to define the myoclonus source in general.…”

“… 27 It is possible that acute PHM can arise from the cortex or a subcortical structure. 26 Indeed, it is hard to determine the origin of myoclonus on the basis of clinical judgment since multiple pathophysiology mechanisms may produce similar clinical phenomena. 12 Hallett et al in 1977 28 described the origin of myoclonus after post-hypoxic injury in the reticular formation of the medulla oblongata and called this “reticular reflex myoclonus.” This type of myoclonus is stimulus sensitive and present at rest; the proximal muscles are more involved than the distal, flexor more than extensor, and it is generalized with initial activation of the muscles innervated by lower brainstem nuclei followed by rostral and caudal recruitment spread.…”