# Clinical Cases: Lower Limb - Neurovasculature

## Case 1: Common Peroneal Nerve Palsy (Foot Drop)

### Clinical Image
![Foot Drop](case_01_image.jpg)
*Source: [Wikimedia Commons - Foot Drop](https://commons.wikimedia.org/wiki/File:Foot_drop.jpg) - CC BY-SA 3.0*

### Case Presentation
A 58-year-old man presents with left foot weakness that he noticed upon waking two days ago. He had been hospitalized for pneumonia the prior week and recalls lying on his left side with his leg against the bedrail for prolonged periods. He reports difficulty lifting his foot when walking and has been tripping over his toes. Physical examination reveals weakness of left ankle dorsiflexion (tibialis anterior, 2/5), toe extension (EHL, EDL, 3/5), and foot eversion (peroneus longus and brevis, 3/5). Ankle plantarflexion (gastrocnemius, soleus) and foot inversion (tibialis posterior) are full strength. There is decreased sensation over the dorsum of the foot and lateral leg. Tinel sign is positive with tapping over the fibular neck. Knee and ankle reflexes are intact. He walks with a steppage gait, lifting his knee high to clear his foot. The clinical presentation is consistent with common peroneal nerve palsy from compression at the fibular neck. EMG/NCS at 3 weeks confirms neurapraxia of the common peroneal nerve. He is fitted with an ankle-foot orthosis (AFO) to prevent tripping and referred for physical therapy. At 3-month follow-up, he has recovered to 4/5 strength with continued improvement expected.

### Key Learning Points
- The common peroneal nerve winds around the fibular neck superficially, making it vulnerable to compression
- The nerve divides into deep peroneal (anterior compartment) and superficial peroneal (lateral compartment) branches
- Peroneal nerve palsy causes foot drop (weakness of dorsiflexion), weak eversion, and dorsal foot sensory loss
- Steppage gait compensates for foot drop by lifting the knee higher to clear the toes
- Common causes: external compression (leg crossing, bed rest, casts), fibular fracture, knee dislocation

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## Case 2: Deep Vein Thrombosis (DVT) of the Lower Extremity

### Clinical Image
![DVT Ultrasound](case_02_image.jpg)
*Source: [Wikimedia Commons - DVT Ultrasound](https://commons.wikimedia.org/wiki/File:DVT_ultrasound.jpg) - CC BY-SA 3.0*

### Case Presentation
A 48-year-old woman presents with 3 days of progressive left leg swelling and pain. She had knee arthroscopy for meniscal repair 2 weeks ago and has been relatively immobile since then. She reports her left calf has been aching and feels "heavy." She denies chest pain, shortness of breath, or hemoptysis. Risk factors include oral contraceptive use and a 6-hour flight 3 weeks before surgery. Physical examination reveals unilateral left lower extremity edema, with the left calf circumference 4 cm greater than the right. The left calf is warm, erythematous, and tender to palpation. Homan sign is positive (calf pain with passive dorsiflexion), though this is unreliable. There is no palpable cord. Venous duplex ultrasound demonstrates a non-compressible left popliteal vein and proximal femoral vein with echogenic material consistent with thrombus. She is diagnosed with acute proximal lower extremity DVT and started on anticoagulation with low-molecular-weight heparin bridged to warfarin. She is educated on DVT prophylaxis and instructed to wear compression stockings.

### Key Learning Points
- The deep veins of the leg include popliteal, femoral, and iliac veins; they accompany the major arteries
- Virchow's triad: stasis, endothelial injury, and hypercoagulability predispose to venous thrombosis
- Proximal DVT (popliteal and above) has higher risk of pulmonary embolism than distal DVT
- Clinical signs include unilateral leg swelling, warmth, erythema, and calf tenderness; Wells criteria guide testing
- Duplex ultrasound with compression is the diagnostic test of choice; inability to compress the vein indicates thrombus

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## Case 3: Femoral Nerve Injury

### Clinical Image
![Femoral Nerve](case_03_image.jpg)
*Source: [Wikimedia Commons - Femoral Nerve](https://commons.wikimedia.org/wiki/File:Femoral_nerve.png) - CC BY-SA 4.0*

### Case Presentation
A 62-year-old man with atrial fibrillation on warfarin presents with sudden onset of right groin pain and anterior thigh numbness following a fall. He reports progressive weakness of his right leg over several hours. His INR is found to be supratherapeutic at 5.2. Physical examination reveals a tender, firm mass in the right groin region. His right leg rests in flexion at the hip. He has marked weakness of knee extension (quadriceps, 2/5) and hip flexion (iliopsoas, 3/5). Sensation is diminished over the anterior thigh (anterior femoral cutaneous) and medial leg (saphenous nerve). The patellar reflex is absent on the right. CT of the pelvis and thigh reveals a large iliopsoas hematoma compressing the femoral nerve within the iliacus compartment. His anticoagulation is reversed with vitamin K and prothrombin complex concentrate. Urgent surgical decompression is performed given the significant motor deficit. Post-operatively, he is enrolled in intensive physical therapy. At 6-month follow-up, he has recovered to 4/5 knee extension strength but continues to have mild sensory deficit.

### Key Learning Points
- The femoral nerve (L2-L4) courses through the iliacus compartment and passes deep to the inguinal ligament
- It innervates iliopsoas (hip flexion), quadriceps (knee extension), and pectineus
- Femoral nerve injury causes weakness of hip flexion and knee extension with loss of patellar reflex
- Sensory distribution: anterior thigh (anterior femoral cutaneous) and medial leg to foot (saphenous nerve)
- Iliopsoas hematoma in anticoagulated patients is a recognized cause of femoral nerve compression