CN - Lower limb mononeuropathies Flashcards
What are lower limb neuropathies?
Conditions where a single peripheral nerve is affected, leading to motor and/or sensory dysfunction in the corresponding area.
Describe a common peroneal (Fibular) nerve mononeuropathy
Common Cause: Compression at the fibular head (often due to prolonged leg crossing, direct trauma, or tight casts), or injury due to fractures or prolonged pressure.
Motor Symptoms: Weakness of dorsiflexion (inability to lift the foot up, leading to foot drop) and eversion of the foot, causing difficulty with walking.
The patient may have a characteristic steppage gait where they lift the leg higher to avoid dragging the foot.
Sensory Symptoms: Numbness or tingling over the dorsum of the foot and the lateral aspect of the lower leg.
Test: Foot drop is the classic sign, with weakness in dorsiflexion and eversion.
Describe a tibial nerve mononeuropathy
Common Cause: Compression or injury at the posterior knee (e.g., in tarsal tunnel syndrome, or due to trauma or prolonged pressure).
Motor Symptoms: Weakness of the plantar flexors (difficulty with toe walking), flexors of the toes (difficulty with toe curling), and inversion of the foot.
Sensory Symptoms: Numbness or tingling along the sole of the foot and the posterior aspect of the leg.
Test: Difficulty with walking on tiptoes or performing toe flexion.
Describe a femoral nerve mononeuropathy
Common Cause: Compression or injury at the inguinal ligament, post-surgical (e.g., after hip surgery), or from trauma.
Motor Symptoms: Weakness of the quadriceps muscle, causing difficulty with knee extension (affecting the ability to straighten the leg). There may also be difficulty with hip flexion.
Sensory Symptoms: Numbness or tingling over the anteromedial thigh and medial aspect of the lower leg.
Test: Weakness of the quadriceps, particularly with knee extension or rising from a seated position.
Describe a obturator nerve mononeuropathy
Common Cause: Compression or injury from pelvic trauma, surgery (such as hip surgery), or tumour-related compression.
Motor Symptoms: Weakness in the adductors of the hip, causing difficulty with adducting the thigh or crossing the legs.
Sensory Symptoms: Numbness over the medial thigh.
Test: Difficulty with hip adduction, or weakness in crossing the legs.
Describe a sciatic nerve mononeuropathy
Common Cause: Compression or injury from trauma (e.g., fractures, dislocations), prolonged sitting, or certain medical procedures (e.g., injections into the gluteal region).
Motor Symptoms: Weakness in the hamstrings, leading to difficulty with knee flexion and loss of foot movement (both dorsiflexion and plantar flexion if both tibial and common peroneal branches are affected). This can lead to foot drop if the common peroneal branch is involved.
Sensory Symptoms: Numbness or tingling in the posterior thigh and lower leg, potentially extending into the foot depending on the level of involvement.
Test: Weakness of knee flexion and possible foot drop. Sciatic nerve involvement can result in loss of sensation in the posterior leg and foot.
Describe a lateral cutaneous nerve of the thigh (Meralgia Paresthetica)
Common Cause: Compression of the nerve as it passes through the inguinal ligament (e.g., from tight clothing, obesity, or pregnancy).
Motor Symptoms: None (this nerve is purely sensory).
Sensory Symptoms: Numbness, tingling, or burning pain over the anterolateral thigh.
Test: Positive Tinel’s sign over the inguinal ligament, with sensory loss over the lateral thigh.
Describe a saphenous nerve mononeuropathy
Common Cause: Often seen after knee surgery, such as ACL repair or varicose vein procedures.
Motor Symptoms: No motor dysfunction (since the saphenous nerve is purely sensory).
Sensory Symptoms: Numbness or tingling along the medial aspect of the leg and the medial ankle.
Test: Sensory loss over the medial lower leg and ankle.
Describe a superior gluteal nerve mononeuropathy
Common Cause: Compression or injury from trauma, hip surgery, or prolonged pressure.
Motor Symptoms: Weakness in the gluteus medius and gluteus minimus muscles, resulting in Trendelenburg gait (a waddling gait) due to inability to stabilize the pelvis during walking.
Sensory Symptoms: Typically none, as this nerve is primarily motor.
Test: Trendelenburg sign, where the pelvis drops on the unaffected side when the patient stands on one leg.
Describe a inferior gluteal nerve mononeuropathy
Common Cause: Injury or compression during hip surgery, trauma, or prolonged pressure.
Motor Symptoms: Weakness of the gluteus maximus muscle, leading to difficulty with hip extension (e.g., rising from a seated position or climbing stairs).
Sensory Symptoms: Typically none, as this nerve is primarily motor.
Test: Difficulty with hip extension, especially during activities like standing up or climbing stairs.
