There was an episode of complete recovery of congenital muscular torticollis presenting an ipsilateral neck mass due to the right sternocleidomastoid muscle (SCM) with other symptoms such as contralateral rotation of the head and restricted motion following initial physiotherapy for 6 months in a male infant. Physical examination and neck ultrasonography in the neonate clinic at 6 months revealed that his neck mass had disappeared, so therapy was discontinued. After 12 months of the episode,

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... re was a reoccurrence of congenital muscular torticollis with the only symptom of ipsilateral neck mass and subsequently recovered without restricted motion. After 26 months of the reoccurrence, with no treatment except for 2 months of the second physiotherapy which was proven to be ineffective, spontaneous resolution of the right neck mass was demonstrated on serial ultrasound. Recovery of relapse SCM hypertrophy is extremely rare; therefore, we report the case. We suggest that the case may help clinicians diagnose and treating patients with the recovery of relapse SCM hypertrophy without complications.