Piriformis Flashcards
1
Q
piriformis actions
A
- straight leg- external rotation at hip
- hip and knee flexed to 90- abduction of hip
2
Q
what exits the piriformis
A
-sacral plexus branches
3
Q
exits superior to piriformis
A
-superior gluteal vessels and n’s
4
Q
exits inferior to piriformis
A
- inf gluteal vessels and n’s
- pudendal vessels and n
- post femoral cutaneous n
- n’s to short external rotators of femur
5
Q
sciatic n- course thru piriformis
A
-inferior- 90% of population!
6
Q
muscle spasm- pathophysiology
A
- m spindle- stretch R
- intrafusal fibers- sensory R’s- monitor length and rate of change in length of extrafusal fibers
- sensory innervation- group 1a afferents
- motor innervation- gamma motor neurons; alpha motor neurons
7
Q
gamma reflex loop
A
- stretch/contraction of m- act gamma motor neuron- causes intrafusal fibers to contract- stretches m spindle- act group 1a afferents- innervates/excites alpha motor neuron- m contraction
- maintains our postural tone
8
Q
gamma loop dysfxn- stretch reflex
A
- sudden stretch of m- stretching of m spindle- act of alpha motor neuron- m contraction- spasm
- sensory signals also go to higher centers of CNS- respond w gamma stim which maintains spasm
9
Q
nociception- spinal cord
A
-nociceptive impulses ascend via contralateral spinothalamic tract
10
Q
nociception- brain
A
- A delta fibers carry impulses to neothalamus and somatosensory cortex- localization/discrmination of pain type
- C fibers- behavior modification, memories
11
Q
nociception- CNS
A
- symp stim- lowers pain threshold
- vasoconstrictoin- “
- NE may sensitize nociceptors- amplifies pain response
12
Q
theory for facilitation
A
- impulse from spinal cord reaches the motor neuron- release of peptides in peripheral tissues- infl cascade
- results in lowering nociceptor thresholds
- infl agents irritate and inflame the epineurium and act nociceptive endings of nevi neuvorum- results in n distribution pain
13
Q
pififormis syndrome
A
- peripheral neuritis of sciatic n caused by abnormal condition of piriformis m
- masquerades as other common SDs
14
Q
epidemiologic considerations
A
- 4-5 decades, women- most common
- primary- anatomic cause
- secondary- precipitating cause
15
Q
Anatomic cause
A
- split piriformis m
- split sciatic n
- anomalous sciatic n path
- <15% of pts
