Quantitative assessment of deficits and recovery of forelimb motor function after cervical spinal cord injury in mice.

A large proportion of spinal cord injuries (SCIs) in humans are at the cervical (C) level, but there are few tests to quantitatively assess forelimb motor function after cervical spinal cord injury in rodents. Here, we describe a simple and reliable technique for assessing forelimb grip strength over time. Female C57Bl/6 mice were trained on the Grip Strength Meter (GSM, TSE-Systems), then received a lateral hemisection of the spinal cord at level C5, C6, C7, or T1. Gripping ability by each forepaw was then tested for 4 weeks postinjury. Before injury, there was no significant difference in the force exerted by either forepaw. After hemisections at C5, C6, or C7, the forepaw ipsilateral to the injury was initially completely unable to grip (day 2 postinjury), and there was a slight transient decrease in the strength of the contralateral paw compared to presurgical levels. The ipsilateral forepaw exhibited no ability to grip until about 10-14 days postlesion, at which time grip reappeared and strength then recovered over a period of a few days to a level that was about 50% of preinjury levels. Grip strength was minimally and transiently affected by hemisection at T1. The grip strength analysis provides a convenient, quantitative measure of the loss and recovery of forelimb function after cervical injury.