Lower Limb Plexi and Sciatica Flashcards
What is a plexus?
Collection of nerve fibres from one source that form ‘new’ nerves with specific targets/destinations
2 plexuses of the lumbosacral plexus
- Lumbar plexus
- Sacral plexus
Where is the lumbosacral plexus located?
Posterior wall of abdomen and pelvis
Where does the lumbar plexus receive input from?
- Anterior rami of nerve roots L1-4
- T12 (subcostal nerve)
In what muscle does the lumbar plexus form?
Psoas
6 branches of lumbar plexus
- I (twice) get late on Fridays:
> Iliohypogastric
> Ilioinguinal
> Genitofemoral
> Lateral cutaneous nerve of thigh
> Obturator
> Femoral
Where does the iliohypogastric nerve emerge in relation to psoas major, and what nerve root supplies it?
- Lateral to psoas major
- Nerve root L1
Where does the ilioinguinal nerve emerge in relation to psoas major, and what nerve root supplies it?
- Lateral to psoas major
- Nerve root L1
Where does the genitofemoral nerve emerge in relation to psoas major, and what nerve root supplies it?
- Anterior to psoas
- Nerve roots L1-2
Where does the lateral cutaneous nerve of the thigh emerge in relation to psoas major, and what nerve root supplies it?
- Lateral to psoas major
- Nerve roots L2-3
Where does the obturator nerve emerge in relation to psoas major, and what nerve root supplies it?
- Medial to psoas
- Nerve roots L2-4
Where does the femoral nerve emerge in relation to psoas major, and what nerve root supplies it?
- Lateral to psoas major
- Nerve roots L2-4
Is each branch of the lumbar plexus sensory only or mixed motor and sensory?
- Iliohypogastric = mixed
- Ilioinguinal = mixed
- Genitofemoral = mixed
- Lateral cutaneous nerve of thigh = sensory only
- Obturator = mixed
- Femoral = mixed
Motor target of each branch of lumbar plexus
- Iliohypogastric = internal oblique, transversus abdominis
- Ilioinguinal = internal oblique, transversus abdominis
- Genitofemoral = male cremasteric muscle
- LCNOT = N/A
- Obturator = obturator externus, pectineus, muscles in medial compartment of thigh
- Femoral = iliacus, pectineus, muscles in anterior compartment of thigh
Where does the sacral plexus receive input from?
- Ventral rami of nerve roots S1-4
- Lumbosacral trunk L4-5
Where is the sacral plexus located?
Superior to piriformis
5 major branches of sacral plexus
- Superior gluteal nerve
- Inferior gluteal nerve
- Sciatic nerve
- Posterior femoral cutaneous nerve
- Pudendal nerve
Where does the superior gluteal nerve receive input from, exit the pelvis, lie and innervate?
- Nerve roots L4-S1
- Greater sciatic foramen above piriformis
- Gluteus minimus
- Gluteus medius, gluteus minimus, tensor fascia lata
Where does the inferior gluteal nerve receive input from, exit the pelvis and innervate?
- Nerve roots L5-S2
- Greater sciatic foramen below piriformis
- Gluteus maximus
Where does the sciatic nerve receive input from and exit the pelvis, and what nerves arise from it?
- Nerve roots L4-S3
- Greater sciatic foramen below piriformis
- Tibial and common peroneal nerves
Where does the posterior femoral cutaneous nerve receive input from, exit the pelvis and provide sensory innervation for?
- Nerve roots S1-3
- Greater sciatic foramen below piriformis
- Posterior thigh, posterior leg, part of perineum
Where does the pudendal nerve receive input from, exit the pelvis, provide motor innervation for and provide sensory innervation for?
- Nerve roots S2-4
- Greater sciatic foramen below piriformis (then back in via lesser foramen)
- Perineum, external urethra, external anal sphincters, levator ani
- Penis/clitoris, most of perineal skin
What does the tibial nerve provide motor innervation to?
- Posterior compartment of thigh (except short head of biceps femoris)
- Adductor magnus
- Posterior compartment of leg
- All muscles in sole of foot
What does the tibial nerve provide sensory innervation to?
- Posterolateral leg
- Sole of foot
What does the common peroneal nerve provide motor innervation to?
- Short head of biceps femoris
- Anterior leg compartment
- Lateral leg compartment
- Extensor digitorum brevis
What does the common peroneal nerve provide sensory innervation to?
- Anterolateral leg
- Dorsum of foot
What is sciatica?
Term used to describe symptoms that present within the distribution of the sciatic nerve
Symptoms of sciatica
- Pain over aspects of thigh or leg
- Numbness/tingling of aspects of thigh or leg
- Weakness of movement of knee or ankle
Causes of sciatica
- Disc prolapse
- Muscle entrapment from piriformis muscle
- Bony spinal pathology (OA, stenosis, spondylolisthesis)
Treatment of sciatica
- Physical therapy
- NSAIDs
- Local steroid injections
- Surgical repair
