Peripheral Nerves in the Lower Extremities

Which of the following nerves is NOT a branch of the lumbar plexus?

Which nerve is formed by the dorsal division of L4-S2?

Which of the following nerves is responsible for the posterior cutaneous sensation of the thigh?

What is the main component of the lumbosacral trunk?

Which of the following nerves is NOT a branch of the sacral plexus?

What is a common cause of lumbosacral plexopathy?

What is the primary functional loss associated with femoral nerve injury?

Which nerve is commonly compressed by a tight piriformis muscle?

What is the primary symptom of tibial nerve injury?

Which of the following is NOT a common site of nerve compression?

What is the primary functional loss associated with sciatic nerve injury?

What is the primary symptom of obturator nerve injury?

What is a common cause of peroneal neuropathy?

What is the primary functional loss associated with tibial nerve injury?

Which nerve is commonly affected in idiopathic lumbosacral plexitis?

Lumbosacral Plexus

The lumbosacral plexus consists of the lumbar plexus (L1-L4) and sacral plexus (S1-S4)
The lumbar plexus forms in the posterior part of the psoas major muscle from the ventral rami of L1-L4

Lumbar Plexus Branches

Femoral nerve
Obturator nerve
Lateral femoral cutaneous nerve
Iliohypogastric nerve
Ilioinguinal nerve
Genitofemoral nerve

Sacral Plexus

Formed by the lumbosacral trunk (L4-L5) and ventral rami of S1-S3

Sacral Plexus Branches

Sciatic nerve (L4-S3)
- Common fibular/peroneal nerve (dorsal division of L4-S2)
- Tibial nerve (ventral division of L4-S3)
Superior gluteal nerve (dorsal L4-S1)
Inferior gluteal nerve (dorsal L5-S2)
Posterior cutaneous nerve of thigh (S1-S3)

Causes of Lumbosacral Plexopathy

Iliacus hematoma (only femoral nerve)
Psoas (retroperitoneal) hematoma
Intrapartum maternal
Pelvic mass
Malignant neoplasms (lymphoma; ovarian, colorectal, and uterine cancer)
Retroperitoneal lymphadenopathy
Abscess
Pelvic fracture
Radiation injury
Diabetes (diabetic amyotrophy, diabetic proximal neuropathy)
Idiopathic lumbosacral plexitis

Peroneal Neuropathy at the Fibular Head

Compression (weight loss, perioperative)
Trauma
Disc herniation
Spinal stenosis
Pelvic surgery
Hematoma
Prolonged labor
Hip surgery
Injection injury
Coma

Clinical Features of Peripheral Nerve Lesions

Ankle inversion: normal, weak, weak, normal or mildly weak
Toe flexion: normal, weak, weak, normal or mildly weak
Plantar flexion: normal, normal, normal, normal or mildly weak
Ankle jerk: normal, normal (unless with S1), normal (unless with S1), normal or depressed

Patterns of Muscle Weakness and Functional Loss

Femoral nerve: illiacus, sartorius, pectineus, quadriceps group
Obturator nerve: obturator externus, adductor muscle group
Sciatic nerve: hamstring group, adductor magnus
Tibial nerve: plantar flexors, popliteus, tibialis posterior, flexor digitorum longus, flexor hallucis longus

This quiz covers the anatomy of the lumbar and sacral plexus, including the formation and branches of the lumbar plexus. It also explores the nerves that emerge from the psoas major muscle, such as the femoral nerve and obturator nerve.