Sensory testing of dermatomes US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Sensory testing of dermatomes. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Sensory testing of dermatomes US Medical PG Question 1: A 25-year-old woman comes to the physician because of pain and weakness in her right forearm and hand for several months. Two years ago, she sustained a fracture of her ulnar shaft with dislocation of the radial head that was treated surgically. Physical examination shows mild tenderness a few centimeters distal to the lateral epicondyle. She has marked weakness when attempting to extend her right middle finger. There is radial deviation on extension of the wrist. Sensation is not impaired. Which of the following nerves is most likely affected in this patient?
- A. Ulnar nerve
- B. Musculocutaneous nerve
- C. Posterior interosseous nerve (Correct Answer)
- D. Superficial radial nerve
- E. Anterior interosseous nerve
Sensory testing of dermatomes Explanation: ***Posterior interosseous nerve***
- The symptoms, including weakness in **middle finger extension** and **radial deviation of the wrist on extension**, are classic signs of **posterior interosseous nerve** (PIN) palsy. This nerve primarily innervates the muscles responsible for **finger and thumb extension**, as well as **extensor carpi ulnaris** (ECU) for wrist extension.
- The **radial deviation on wrist extension** occurs because the radial-sided wrist extensors (**extensor carpi radialis longus** and **brevis**) are innervated by the **radial nerve proper** before it branches into PIN, so they remain intact. With loss of ECU (ulnar-sided wrist extensor), unopposed action of ECRL and ECRB causes radial deviation.
- PIN palsy can result from **trauma** or compression, and the patient's history of a **radial head dislocation** two years prior is a significant risk factor for nerve damage in this region, particularly as PIN passes through the **supinator muscle** (arcade of Frohse). Tenderness distal to the **lateral epicondyle** also points to the region where PIN can be compressed.
*Ulnar nerve*
- An **ulnar nerve** injury would primarily cause weakness in **finger adduction and abduction** (especially the little finger and ring finger), **flexion of the ulnar half of the profundus**, and **intrinsic hand muscles**, leading to a "claw hand" deformity if severe.
- Sensation would also be affected in the **palmar and dorsal aspects of the 5th digit** and the **medial half of the 4th digit**, which is not described.
*Musculocutaneous nerve*
- The **musculocutaneous nerve** primarily innervates the **biceps brachii** and **brachialis muscles**, responsible for **elbow flexion** and **forearm supination**.
- Sensory deficits would be noted on the **lateral forearm**, none of which align with the patient's symptoms.
*Superficial radial nerve*
- The **superficial radial nerve** is purely sensory and provides sensation to the **dorsum of the hand** and parts of the thumb, index, and middle fingers.
- It does not have any motor function, so motor weakness would not be a symptom of its injury.
*Anterior interosseous nerve*
- The **anterior interosseous nerve** (AIN) is a purely motor branch of the median nerve, responsible for innervating the **flexor pollicis longus**, **flexor digitorum profundus (index and middle fingers)**, and **pronator quadratus**.
- Injury to the AIN would result in an inability to form an "OK" sign (due to impaired flexion of the thumb IP joint and index finger DIP joint) and no sensory loss.
Sensory testing of dermatomes US Medical PG Question 2: A 51-year-old woman comes to the physician because of progressively worsening lower back pain. The pain radiates down the right leg to the lateral side of the foot. She has had no trauma, urinary incontinence, or fever. An MRI of the lumbar spine shows disc degeneration and herniation at the level of L5–S1. Which of the following is the most likely finding on physical examination?
- A. Difficulty walking on heels
- B. Exaggerated patellar tendon reflex
- C. Diminished sensation of the anus and genitalia
- D. Diminished sensation of the anterior lateral thigh
- E. Weak Achilles tendon reflex (Correct Answer)
Sensory testing of dermatomes Explanation: ***Weak Achilles tendon reflex***
- A herniated disc at **L5-S1** typically compresses the **S1 nerve root**, which is responsible for the **Achilles tendon reflex**.
- **S1 radiculopathy** presents with weakness in plantarflexion, diminished or absent Achilles reflex, and sensory loss in the **lateral foot** (matching the patient's symptoms).
*Difficulty walking on heels*
- Difficulty walking on heels (**dorsiflexion weakness**) is primarily associated with **L4-L5 disc herniation** compressing the **L5 nerve root**.
- This symptom indicates **L5 radiculopathy**, which affects the tibialis anterior muscle, not S1.
*Exaggerated patellar tendon reflex*
- An exaggerated patellar tendon reflex (**hyperreflexia**) indicates an **upper motor neuron lesion** or spinal cord compression above the lumbar region.
- A disc herniation at **L5-S1** causes a **lower motor neuron lesion** with diminished reflexes, not hyperreflexia.
*Diminished sensation of the anus and genitalia*
- This symptom, along with urinary incontinence and saddle anesthesia, is characteristic of **cauda equina syndrome**, a surgical emergency.
- The patient lacks urinary incontinence and the specific unilateral pain pattern points to isolated **S1 radiculopathy**, not cauda equina syndrome.
*Diminished sensation of the anterior lateral thigh*
- Sensory loss in the **anterior lateral thigh** is associated with compression of the **lateral femoral cutaneous nerve** or **L2-L4 nerve roots**.
- This pattern is not consistent with **L5-S1 disc herniation**, which causes sensory changes in the lateral foot and posterior leg.
Sensory testing of dermatomes US Medical PG Question 3: A 29-year-old woman presents to the primary care office for a recent history of falls. She has fallen 5 times over the last year. These falls are not associated with any preceding symptoms; she specifically denies dizziness, lightheadedness, or visual changes. However, she has started noticing that both of her legs feel weak. She's also noticed that her carpet feels strange beneath her bare feet. Her mother and grandmother have a history of similar problems. On physical exam, she has notable leg and foot muscular atrophy and 4/5 strength throughout her bilateral lower extremities. Sensation to light touch and pinprick is decreased up to the mid-calf. Ankle jerk reflex is absent bilaterally. Which of the following is the next best diagnostic test for this patient?
- A. MRI brain
- B. Ankle-brachial index
- C. Electromyography (including nerve conduction studies) (Correct Answer)
- D. Lumbar puncture
- E. Hemoglobin A1c
Sensory testing of dermatomes Explanation: ***Electromyography (including nerve conduction studies)***
- The patient's symptoms of **progressive weakness**, **sensory deficits** (carpet feels strange, decreased sensation up to mid-calf), **muscular atrophy**, and **absent ankle reflexes**, along with a **family history**, are highly suggestive of a **hereditary peripheral neuropathy** (e.g., Charcot-Marie-Tooth disease).
- **Electromyography (EMG)** and **nerve conduction studies (NCS)** are essential for confirming peripheral neuropathy, differentiating between demyelinating and axonal involvement, and localizing the lesion.
*MRI brain*
- An MRI brain would be indicated for central nervous system pathology, but the patient's symptoms (distal weakness, sensory loss with a "stocking-glove" distribution, absent reflexes) are highly suggestive of a **peripheral neuropathy**.
- There is no indication of upper motor neuron signs or other CNS involvement to warrant a brain MRI at this stage.
*Ankle-brachial index*
- Ankle-brachial index (ABI) is used to diagnose **peripheral artery disease (PAD)**, which typically presents with claudication (pain with exertion) and ischemic changes.
- The patient's symptoms of sensory changes and progressive weakness are not characteristic of PAD.
*Lumbar puncture*
- A lumbar puncture is primarily used to analyze **cerebrospinal fluid (CSF)** for inflammatory, infectious, or neoplastic conditions affecting the CNS or nerve roots (e.g., Guillain-Barré syndrome, which has acute onset).
- Given the chronic and progressive nature of her symptoms and a positive family history, it is less likely to be an acute inflammatory process of the nerve roots.
*Hemoglobin A1c*
- Hemoglobin A1c is used to screen for or monitor **diabetes mellitus**, which can cause a **diabetic neuropathy**.
- While diabetes can cause peripheral neuropathy, the patient's young age, lack of typical diabetic risk factors, and strong family history point more strongly towards a hereditary condition. Glycemic control does not fully explain her presentation.
Sensory testing of dermatomes US Medical PG Question 4: A 72-year-old woman is brought in to the emergency department after her husband noticed that she appeared to be choking on her dinner. He performed a Heimlich maneuver but was concerned that she may have aspirated something. The patient reports a lack of pain and temperature on the right half of her face, as well as the same lack of sensation on the left side of her body. She also states that she has been feeling "unsteady" on her feet. On physical exam you note a slight ptosis on the right side. She is sent for an emergent head CT. Where is the most likely location of the neurological lesion?
- A. Pons
- B. Internal capsule
- C. Cervical spinal cord
- D. Medulla (Correct Answer)
- E. Midbrain
Sensory testing of dermatomes Explanation: ***Medulla***
- This presentation describes **Wallenberg syndrome** (lateral medullary syndrome), characterized by **ipsilateral facial sensory loss**, **contralateral body sensory loss**, and **ataxia** due to involvement of the spinothalamic tracts, trigeminal nucleus, and cerebellar pathways.
- **Dysphagia** (choking) and **Horner's syndrome** (ptosis, miosis, anhidrosis) are also classic signs, specifically the ptosis seen here, pointing to an infarct in the **lateral medulla**.
*Pons*
- Lesions in the pons typically present with varying degrees of **cranial nerve deficits** (e.g., trigeminal, abducens, facial) and **motor or sensory deficits** affecting both sides of the body due to the decussation of tracts.
- The specific combination of **crossed sensory loss** and other symptoms seen here is not characteristic of isolated pontine lesions.
*Internal capsule*
- A lesion in the internal capsule would primarily cause **contralateral motor weakness (hemiparesis)** and **sensory loss** affecting both the face and body on the same side, without the ipsilateral facial involvement.
- It would not explain the **ataxia** or specific cranial nerve signs like ptosis.
*Cervical spinal cord*
- Spinal cord lesions result in **sensory and motor deficits below the level of the lesion**, affecting both sides of the body symmetrically, or ipsilaterally depending on the tract involved.
- They do not cause **facial sensory disturbances**, **dysphagia**, or **ataxia** in the manner described.
*Midbrain*
- Midbrain lesions typically involve the **oculomotor nerve** (CN III), causing eye movement abnormalities, and can result in **contralateral hemiparesis**.
- They do not produce the **crossed sensory deficits** (ipsilateral face, contralateral body) or **ataxia** characteristic of this case.
Sensory testing of dermatomes US Medical PG Question 5: A 40-year-old woman presents with a ‘tingling’ feeling in the toes of both feet that started 5 days ago. She says that the feeling varies in intensity but has been there ever since she recovered from a stomach flu last week. Over the last 2 days, the tingling sensation has started to spread up her legs. She also reports feeling weak in the legs for the past 2 days. Her past medical history is unremarkable, and she currently takes no medications. Which of the following diagnostic tests would most likely be abnormal in this patient?
- A. Noncontrast CT of the head
- B. Serum hemoglobin concentration
- C. Nerve conduction studies (Correct Answer)
- D. Serum calcium concentration
- E. Transthoracic echocardiography
Sensory testing of dermatomes Explanation: ***Nerve conduction studies***
- The patient's ascending **motor weakness** and **sensory paresthesias** following a gastrointestinal infection are classic symptoms of **Guillain-Barré Syndrome (GBS)**, which is characterized by **demyelination** of peripheral nerves.
- **Nerve conduction studies** would reveal **markedly slowed conduction velocities**, **conduction block**, and **prolonged distal latencies**, indicating the demyelinating neuropathy characteristic of GBS.
*Noncontrast CT of the head*
- This test is primarily used to evaluate **acute neurological deficits** suggestive of stroke, hemorrhage, or mass lesions within the brain.
- The patient's symptoms are consistent with a **peripheral neuropathy** and do not suggest a central nervous system pathology.
*Serum hemoglobin concentration*
- This measures the concentration of **hemoglobin in the blood** and is used to diagnose **anemia**.
- While anemia can cause fatigue, it does not typically cause the **ascending paralysis** and **paresthesias** described, nor is it directly related to a recent stomach flu in this manner.
*Serum calcium concentration*
- This measures the level of **calcium in the blood**, which is important for muscle and nerve function.
- While extreme imbalances can cause neurological symptoms, there is no direct indication or typical association between the patient's symptoms and a primary calcium disorder.
*Transthoracic echocardiography*
- This imaging test evaluates the **structure and function of the heart**.
- The patient's symptoms are neurological and do not suggest a primary cardiac etiology or complication that would warrant an echocardiogram.
Sensory testing of dermatomes US Medical PG Question 6: A 59-year-old woman presents to the emergency room with severe low back pain. She reports pain radiating down her left leg into her left foot. She also reports intermittent severe lower back spasms. The pain started after lifting multiple heavy boxes at her work as a grocery store clerk. She denies bowel or bladder dysfunction. Her past medical history is notable for osteoporosis and endometrial cancer. She underwent a hysterectomy 20 years earlier. She takes alendronate. Her temperature is 99°F (37.2°C), blood pressure is 135/85 mmHg, pulse is 85/min, and respirations are 22/min. Her BMI is 21 kg/m^2. On exam, she is unable to bend over due to pain. Her movements are slowed to prevent exacerbating her muscle spasms. A straight leg raise elicits severe radiating pain into her left lower extremity. The patient reports that the pain is worst along the posterior thigh and posterolateral leg into the fourth and fifth toes. Palpation along the lumbar vertebral spines demonstrates mild tenderness. Patellar reflexes are 2+ bilaterally. The Achilles reflex is decreased on the left. Which nerve root is most likely affected in this patient?
- A. L5
- B. S2
- C. L3
- D. L4
- E. S1 (Correct Answer)
Sensory testing of dermatomes Explanation: ***S1***
- Pain radiating to the **posterior thigh**, **posterolateral leg**, and into the **fourth and fifth toes** is characteristic of **S1 dermatome involvement**.
- A **decreased Achilles reflex** (ankle jerk reflex) specifically points to compromise of the **S1 nerve root**.
*L5*
- **L5 radiculopathy** typically causes pain and sensory deficits in the **dorsum of the foot** and into the **first, second, and third toes**.
- Motor weakness often affects **foot dorsiflexion** and **toe extension**, not primarily the Achilles reflex.
*S2*
- **S2 radiculopathy** would primarily affect sensation along the **posterior thigh** and **calf**, with possible involvement of the **plantar aspect of the foot**.
- It does not typically cause a decrease in the **Achilles reflex**, which is predominantly S1.
*L3*
- **L3 radiculopathy** typically presents with pain and sensory changes along the **anterior thigh** and possibly the **medial knee**.
- It can affect the **patellar reflex**, which is intact in this patient, and does not cause pain in the posterior leg or foot.
*L4*
- **L4 radiculopathy** typically causes pain and sensory changes over the **anterior thigh**, **medial leg**, and potentially the **medial malleolus**.
- It often presents with weakness in **quadriceps muscle** and can cause a diminished **patellar reflex**, which is normal in this patient.
Sensory testing of dermatomes US Medical PG Question 7: A 75-year-old man comes to the physician because of a 2-week history of sharp, stabbing pain in the lower back that radiates to the back of his left leg. He also has had a loss of sensitivity around his buttocks and inner thighs as well as increased trouble urinating the last week. Two years ago, he was diagnosed with prostate cancer and was treated with radiation therapy. Neurologic examination shows reduced strength and reflexes in the left lower extremity; the right side is normal. The resting anal sphincter tone is normal but the squeeze tone is reduced. Which of the following is the most likely diagnosis?
- A. Central cord syndrome
- B. Conus medullaris syndrome
- C. Anterior spinal cord syndrome
- D. Brown-sequard syndrome
- E. Cauda equina syndrome (Correct Answer)
Sensory testing of dermatomes Explanation: ***Cauda equina syndrome***
- The patient presents with **bilateral sensory loss in the perineal region** (**saddle anesthesia**) and **new-onset urinary dysfunction** (trouble urinating, reduced squeeze tone), which are classic symptoms of cauda equina syndrome.
- The **sharp, stabbing radicular pain** radiating down the leg indicates nerve root involvement, characteristic of cauda equina rather than conus medullaris.
- The **asymmetric motor weakness** (left leg only) supports cauda equina syndrome, as compression can preferentially affect specific nerve roots, whereas conus medullaris typically causes more symmetric bilateral deficits.
- The history of **prostate cancer** and **radiation therapy** suggests a potential metastatic lesion compressing the cauda equina nerves.
*Central cord syndrome*
- This syndrome primarily affects the **upper extremities more than the lower extremities** and typically results from hyperextension injuries in older individuals.
- It often presents with **dissociated sensory loss** (loss of pain and temperature sensation) below the level of the lesion, which is not the primary complaint here.
*Conus medullaris syndrome*
- Affects the **sacral spinal cord segments (S3-S5)**, leading to **symmetrical motor and sensory deficits**, often with prominent early **bowel and bladder dysfunction**.
- While it causes saddle anesthesia and urinary symptoms, the **asymmetrical motor weakness** (left leg only) and **prominent radicular pain** extending down the leg are more characteristic of cauda equina syndrome.
- Conus lesions typically present with more **symmetric bilateral deficits** rather than the unilateral pattern seen here.
*Anterior spinal cord syndrome*
- Characterized by **bilateral motor paralysis** and **loss of pain and temperature sensation** below the lesion, with **preservation of proprioception and vibratory sensation**.
- It would not typically present with the isolated **saddle anesthesia** and **radicular pain** described in the patient.
*Brown-sequard syndrome*
- Results from a **hemicord lesion**, causing **ipsilateral motor paralysis** and loss of proprioception/vibration below the lesion, and **contralateral loss of pain and temperature sensation**.
- The patient's symptoms of **bilateral saddle anesthesia** and **bowel/bladder dysfunction** do not align with the characteristic unilateral sensory and motor presentation of Brown-Sequard syndrome.
Sensory testing of dermatomes US Medical PG Question 8: A 35-year-old woman, gravida 2, para 1, at 40 weeks' gestation, presents to the hospital with contractions spaced 2 minutes apart. Her past medical history is significant for diabetes, which she has controlled with insulin during this pregnancy. Her pregnancy has otherwise been unremarkable. A baby boy is born via a spontaneous vaginal delivery. Physical examination shows he weighs 4.5 kg (9 lb), the pulse is 140/min, the respirations are 40/min, and he has good oxygen saturation on room air. His left arm is pronated and medially rotated. He is unable to move it away from his body. The infant’s right arm functions normally and he is able to move his wrists and all 10 digits. Which of the following nerve roots were most likely damaged during delivery?
- A. C4 and C5
- B. C7 and C8
- C. C5 and C6 (Correct Answer)
- D. C8 and T1
- E. C6 and C7
Sensory testing of dermatomes Explanation: ***C5 and C6***
- The presentation of the infant's left arm being **pronated**, **medially rotated**, and unable to be moved away from the body is characteristic of **Erb-Duchenne palsy** (also called "waiter's tip" deformity).
- This condition results from damage to the **upper trunk of the brachial plexus**, specifically involving the **C5 and C6 nerve roots**.
- These roots innervate muscles responsible for **shoulder abduction** (deltoid, supraspinatus), **external rotation** (infraspinatus), and **elbow flexion/supination** (biceps brachii).
- The preserved wrist and digit function confirms the injury is limited to the upper trunk, sparing C7-T1.
*C4 and C5*
- While C5 is involved in Erb's palsy, the **C4 root** primarily contributes to the **phrenic nerve** (diaphragm innervation) and provides sensation to the neck and shoulder region.
- C4 does not significantly contribute to the brachial plexus motor function, so damage to C4 would not explain the shoulder and elbow deficits observed.
*C7 and C8*
- Damage to **C7 and C8** would primarily affect **wrist extension** (C7) and **finger flexion** (C8), not the shoulder abduction and elbow flexion deficits seen here.
- This pattern would be inconsistent with Erb's palsy and more suggestive of middle-to-lower trunk injury.
*C8 and T1*
- Injury to **C8 and T1** nerve roots causes **Klumpke's palsy**, affecting the **intrinsic hand muscles** and wrist flexors, leading to a "claw hand" deformity.
- The infant's preserved ability to move all wrists and digits rules out C8-T1 injury, as this would severely impair hand function and potentially cause **Horner's syndrome** (if T1 is involved).
*C6 and C7*
- While **C6** is involved in Erb's palsy, adding **C7** damage would extend the injury to affect **wrist extensors** (extensor carpi radialis) and **triceps** (elbow extension).
- The clinical presentation described is most consistent with isolated upper trunk (C5-C6) injury, not extended involvement of C7.
Sensory testing of dermatomes US Medical PG Question 9: A 58-year-old diabetic man with multiple thoracic vertebral compression fractures presents with progressive lower extremity dysfunction. He has spastic paraparesis with hyperreflexia, bilateral Babinski signs, and a sensory level at T10. However, he also has areflexic bladder, saddle anesthesia, and absent bulbocavernosus reflex. Upper extremities are completely normal. Synthesize the anatomical explanation for this mixed upper and lower motor neuron presentation.
- A. Complete spinal cord transection at T10 level
- B. Conus medullaris syndrome with additional cord compression (Correct Answer)
- C. Cauda equina syndrome with coincidental cord pathology
- D. Combined central cord and conus medullaris injury
- E. Diabetic lumbosacral radiculoplexus neuropathy with cord compression
Sensory testing of dermatomes Explanation: ***Conus medullaris syndrome with additional cord compression***
- The **conus medullaris** represents the terminal end of the spinal cord (L1-L2), where damage causes a mix of **UMN signs** (from the cord itself) and **LMN signs** (from exiting sacral roots).
- This patient exhibits **UMN signs** (spasticity, hyperreflexia, Babinski) from cord compression at T10, alongside **LMN signs** (areflexic bladder, saddle anesthesia, absent bulbocavernosus reflex) specific to the **conus/sacral segments**.
*Complete spinal cord transection at T10 level*
- A complete transection at T10 would cause **pure UMN signs** below the level of the lesion and would not selectively cause isolated **areflexic bladder** or **saddle anesthesia** typical of conus/root injury.
- It would typically result in a **spastic bladder** over time once the period of spinal shock has resolved, unlike this patient's LMN presentation.
*Cauda equina syndrome with coincidental cord pathology*
- **Cauda equina syndrome** involves compression of lumbosacral nerve roots and results in a **pure LMN lesion** without Babinski signs or hyperreflexia.
- While cord pathology could explain UMN signs, the specific clustering of sacral symptoms with thoracic compression points more directly to the **conus medullaris** transition zone.
*Combined central cord and conus medullaris injury*
- **Central cord syndrome** almost exclusively affects the **cervical spine**, leading to upper extremity weakness greater than lower extremity weakness.
- Since the patient's **upper extremities** are normal, a central cord mechanism is anatomically inconsistent with this presentation.
*Diabetic lumbosacral radiculoplexus neuropathy with cord compression*
- **Diabetic radiculoplexus neuropathy** (amyotrophy) typically presents with **acute, asymmetric thigh pain** and proximal muscle wasting, which is not described here.
- While diabetes is a risk factor for neuropathies, it does not explain the anatomical clustering of **saddle anesthesia** and **absent bulbocavernosus reflex** as precisely as a conus lesion.
Sensory testing of dermatomes US Medical PG Question 10: A 42-year-old office worker develops progressive bilateral leg pain, weakness, and numbness over months. Examination reveals asymmetric weakness: right leg has weak hip flexion and knee extension with diminished patellar reflex; left leg has weak ankle dorsiflexion and toe extension with normal reflexes. Sensory examination shows patchy loss in L4 distribution on the right and L5 distribution on the left. MRI shows multilevel degenerative disc disease at L3-L4 and L4-L5 with foraminal stenosis. Evaluate the pathophysiological explanation for this clinical pattern.
- A. Sequential nerve root compression at different levels bilaterally
- B. Unilateral L4 radiculopathy with contralateral L5 radiculopathy (Correct Answer)
- C. Bilateral L5 radiculopathy with asymmetric presentation
- D. Central canal stenosis with differential nerve root vulnerability
- E. Polyradiculopathy from inflammatory or infiltrative process
Sensory testing of dermatomes Explanation: ***Unilateral L4 radiculopathy with contralateral L5 radiculopathy***
- The right-sided weakness in **hip flexion (L2-L4)** and **knee extension (L3-L4)**, combined with a diminished **patellar reflex**, specifically localizes to the **L4 nerve root**.
- The left-sided weakness in **ankle dorsiflexion** and **toe extension (L5)**, alongside an L5 sensory deficit, confirms a separate, contralateral involvement of the **L5 nerve root** due to **foraminal stenosis**.
*Sequential nerve root compression at different levels bilaterally*
- While the pathology is multilevel, this option lacks the anatomic specificity required to define the distinct **L4 vs. L5** deficits observed on exam.
- The term "sequential" implies a temporal progression that is less clinically precise than identifying the specific **radiculopathies** involved.
*Bilateral L5 radiculopathy with asymmetric presentation*
- Bilateral L5 involvement would not explain the **diminished patellar reflex** on the right, which is a hallmark of **L4 nerve root** dysfunction.
- L5 radiculopathy typically affects **hip abduction** and **foot inversion**, whereas this patient has deficits clearly localizing to **higher lumbar levels** on the right.
*Central canal stenosis with differential nerve root vulnerability*
- **Central stenosis** usually presents as **neurogenic claudication** which is typically more symmetric and relieved by leaning forward.
- The MRI specifically noted **foraminal stenosis**, which is the classic cause of **radiculopathy** (exit nerve root compression) rather than the cauda equina compression seen in central stenosis.
*Polyradiculopathy from inflammatory or infiltrative process*
- Inflammatory processes like **Guillain-Barré** or malignancy usually present with more rapid progression or systemic symptoms not seen here.
- The clinical findings are better explained by the **mechanical compression** from **degenerative disc disease** and stenosis clearly visible on the MRI.
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