Dermatomes! (YAY!) Also see FA2020 p452 for lower extremity nerves.
T10 dermatome is the level of the umbilicus.
L1/L2 would be upper medial and anterior thigh, not down to the foot. The most common buzzwords for injury (less likely via the mechanism in this question) would be absent cremasteric reflex as this is where the genitofemoral nerve originates. The cremasteric nerve is usually injured in laproscopic surgery.
L3/4 is correct because this cooresponds to the correct dermatome for the shooting pain.
S1/2 is associated with sciatica (sciatic nerve is L4-S3), which would be a shooting pain beginning in the buttocks and shooting down to the heel (see dermatomes). This is not described here. Also this is less likely because the sacral spinal cord is fused and less likely to get bony outgrowths. The most common cause of sciatica is an L5 bulging disc causing S1 compression.
S4/5 injury is associated with perianal numbness and potential fecal incontenence(pudendal nerve is S2-S4). However this injury would not be atypical because the sacral spinal cord is fused and less likely to have bony outgrowths causing compression.
waitingonprometricI answered this question a little differently, and it might help someone! I thought about the description of the dermatome going over the knee joint in terms of what reflexes the nerves there would be mediating. i.e. this would be the area of the nerves that mediate the patellar reflex, which is L2-L4, hence the answer.
The pnemonic I always use for reflexes is:
S1-S2 "buckle my shoe" (Achilles reflex)
L2-L4 "kick the door" (patellar reflex)
C5-C6 "pick up sticks" (biceps reflex)
C7-C8 "lay them straight" (triceps reflex)
L1-L2 "testicles move" (cremaster reflex)
S3-S4 "winks galore" (anal wink reflex)+15
passplease@cassdawg thank you for the explanation. Can you please explain (or point me to the source) about the sacral spinal cord being fused and less likely to get bony outgrowths? Thank you!!+7
submitted by โcassdawg(1780)
Dermatomes! (YAY!) Also see FA2020 p452 for lower extremity nerves.
T10 dermatome is the level of the umbilicus.
L1/L2 would be upper medial and anterior thigh, not down to the foot. The most common buzzwords for injury (less likely via the mechanism in this question) would be absent cremasteric reflex as this is where the genitofemoral nerve originates. The cremasteric nerve is usually injured in laproscopic surgery.
L3/4 is correct because this cooresponds to the correct dermatome for the shooting pain.
S1/2 is associated with sciatica (sciatic nerve is L4-S3), which would be a shooting pain beginning in the buttocks and shooting down to the heel (see dermatomes). This is not described here. Also this is less likely because the sacral spinal cord is fused and less likely to get bony outgrowths. The most common cause of sciatica is an L5 bulging disc causing S1 compression.
S4/5 injury is associated with perianal numbness and potential fecal incontenence(pudendal nerve is S2-S4). However this injury would not be atypical because the sacral spinal cord is fused and less likely to have bony outgrowths causing compression.