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