Characterization of growth and survival of mice displaying early onset hypertonic symptoms is critical as these animals are important for research investigating mech-anisms and treatments of pediatric conditions associated with hypertonia, such as cerebral palsy. Currently, most animal models of cerebral palsy reproduce risk factors for developing this condition, with most failing to develop the physical symptoms or failing to survive in the postnatal period. The B6.Cg- Glrb spa /J (Gly receptor mutation) transgenic mouse ( spa mouse), displays symptoms of early onset hypertonia, though little has been reported on growth and survival, with no reports of growth and sur-vival since genotyping became available. We found that the majority of spa mice dis-play symptoms by P14-P16. Of mice surviving to weaning, only ～9％ were spa mice. By weaning age, spa mice had significantly lower weights than their heterozygote and wild-type littermates. Of mice that died after weaning and prior to use in experi-ments or being culled, 48％ were spa mice. The poor growth and decreased survival of spa mice across multiple developmental and adult ages resembled the varied sur-vival rates observed in humans with mild or severe cerebral palsy. The understanding of the expected survival of these mice is helpful for planning breeding and animal numbers for experiments. Due to the symptoms and timing of symptom onset, spa mice will be valuable in uncovering mechanisms and long-term effects of early onset hypertonia in order to move toward interventions for these conditions.