Neurology · MU Sofia

39. Diseases of the lumbar and sacral roots and lumbar and sacral plexus

Covers damage to the lumbar and sacral nerve roots, with their causes such as disc herniation, stenosis, tumours, trauma and infection, then the root syndrome pattern of radicular pain, dermatomal sensory loss, myotomal weakness and reflex change. It goes on to lumbar plexus lesions (femoral, obturator and lateral femoral cutaneous nerves) and sacral plexus lesions (sciatic, common peroneal, tibial and pudendal nerves). A closing table compares root, plexus and peripheral nerve lesions by pain, sensory, motor and reflex features.

Inside: 4 sections · 4 tables · 15 flashcards · 2 min

Topic 39 of 88 in the MU Sofia syllabus for Neurology (Medicine, Year 4). The free AceMed note covers it in 4 sections, about 232 words (2 min of reading), with 15 flashcards.

In this note

  1. Diseases of the lumbar and sacral roots and lumbar and sacral plexus
  2. Lumbar Plexus Lesions (L1–L4)
  3. Sacral Plexus Lesions (L4–S4)
  4. Plexus vs Root vs Peripheral Nerve

Diseases of the lumbar and sacral roots and lumbar and sacral plexus

1. Lumbar & Sacral Root Lesions (Radiculopathy)

Definition: Damage to lumbar (L1–L5) or sacral (S1–S5) nerve roots, causing segmental motor, sensory, and reflex deficits.

Causes: Lumbar disc herniation (most common). Spondylosis / spinal stenosis. Tumors (metastasis). Trauma. Infections (radiculitis)

Clinical Features (Root Syndrome)

1. Pain: Severe radicular (shooting) pain. Radiates along dermatome. Worsened by coughing, sneezing, movement

2. Sensory Loss: Dermatomal pattern. Paresthesia, numbness

3. Motor Deficit (Myotomal)

4. Reflex Changes

Lumbar Plexus Lesions (L1–L4)

Main Nerves: Femoral nerve. Obturator nerve. Lateral femoral cutaneous nerve

A. Femoral Nerve Lesion

Features: Weak knee extension. Loss of patellar reflex. Sensory loss anterior thigh + medial leg. Difficulty climbing stairs

B. Obturator Nerve Lesion

Features: Weak thigh adduction. Instability while walking. Medial thigh sensory loss

C. Lateral Femoral Cutaneous Nerve (Meralgia Paresthetica)

Features: Burning pain/paresthesia in lateral thigh. No motor deficit. Compression under inguinal ligament

Sacral Plexus Lesions (L4–S4)

Main Nerves: Sciatic nerve (tibial + peroneal). Pudendal nerve. Superior/inferior gluteal nerves

A. Sciatic Nerve Lesion

Features: Weak knee flexion. Weak ankle movements. Foot drop (if peroneal division affected). Sensory loss posterior thigh + leg + foot

B. Common Peroneal Nerve Palsy

Features: Foot drop. Weak dorsiflexion. High-stepping gait. Sensory loss lateral leg + dorsum foot

C. Tibial Nerve Lesion

Features: Weak plantar flexion. Difficulty standing on toes. Loss of Achilles reflex. Sensory loss sole of foot

D. Pudendal Nerve Lesion (S2–S4)

Features: Loss of anal sphincter control. Urinary/fecal incontinence. Sexual dysfunction. Saddle anesthesia

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