Skeletal radiologic landmarks — MCQs

10 questions

A 23-year-old man complains of lower back pain that began approximately 6 months ago. He is unsure why he is experiencing this pain and notices that this pain is worse in the morning after waking up and improves with physical activity. Ibuprofen provides significant relief. He denies bowel and bladder incontinence or erectile dysfunction. Physical exam is notable for decreased chest expansion, decreased spinal range of motion, 5/5 strength in both lower extremities, 2+ patellar reflexes bilaterally, and an absence of saddle anesthesia. Which of the following is the most appropriate next test for this patient?

A 33-year-old man presents to his primary care physician with shoulder pain. He states that he can't remember a specific instance when the injury occurred. He is a weight lifter and competes in martial arts. The patient has no past medical history and is currently taking a multivitamin. Physical exam demonstrates pain with abduction of the patient's right shoulder and with external rotation of the right arm. There is subacromial tenderness with palpation. His left arm demonstrates 10/10 strength with abduction as compared to 4/10 strength with abduction of the right arm. Which of the following best confirms the underlying diagnosis?

A 50-year-old man presents with severe chest pain for a week. His pain increases with breathing and is localized to the right. He has tried over-the-counter medications at home, but they did not help. The patient has a 20-pack-year smoking history and currently smokes 2 packs of cigarettes daily, and he drinks 3 to 4 cans of beer daily before dinner. His temperature is 39.1°C (102.3°F), blood pressure is 127/85 mm Hg, pulse is 109/min, and respirations are 20/min. Respiratory examination shows dullness to percussion from the 7th rib inferiorly at the right midaxillary line, decreased vocal tactile fremitus, and diminished breath sounds in the same area. Chest radiograph is shown in the image. The patient is prepared for thoracocentesis. Which of the following locations would be the most appropriate for insertion of a chest tube?

A 22-year-old man is rushed to the emergency department after a motor vehicle accident. The patient states that he feels weakness and numbness in both of his legs. He also reports pain in his lower back. His airway, breathing, and circulation is intact, and he is conversational. Neurologic exam is significant for bilateral lower extremity flaccid paralysis and impaired pain and temperature sensation up to T10-T11 with normal vibration sense. A computerized tomography scan of the spine is performed which shows a vertebral burst fracture of the vertebral body at the level of T11. Which of the following findings is most likely present in this patient?

A 69-year-old woman presents with pain in her hip and groin. She states that the pain is present in the morning, and by the end of the day it is nearly unbearable. Her past medical history is notable for a treated episode of acute renal failure, diabetes mellitus, obesity, and hypertension. Her current medications include losartan, metformin, insulin, and ibuprofen. The patient recently started taking high doses of vitamin D as she believes that it could help her symptoms. She also states that she recently fell off the treadmill while exercising at the gym. On physical exam you note an obese woman. There is pain, decreased range of motion, and crepitus on physical exam of her right hip. The patient points to the areas that cause her pain stating that it is mostly over the groin. The patient's skin turgor reveals tenting. Radiography is ordered. Which of the following is most likely to be found on radiography?

A 45-year-old man presents for a follow-up visit as part of his immigration requirements into the United States. Earlier this week, he was administered the Mantoux tuberculin skin test (TST). Today’s reading, 3 days after being administered the test, he shows an induration of 10 mm. Given his recent immigration from a country with a high prevalence of tuberculosis, he is requested to obtain a radiograph of the chest, which is shown in the image. Which of the following is true regarding this patient’s chest radiograph (CXR)?

A 33-year-old woman presents to the emergency department with pain in her right wrist. She says she was walking on the sidewalk a few hours ago when she suddenly slipped and landed forcefully on her outstretched right hand with her palm facing down. The patient is afebrile, and vital signs are within normal limits. Physical examination of her right wrist shows mild edema and tenderness on the lateral side of the right hand with a decreased range of motion. Sensation is intact. The patient is able to make a fist and OK sign with her right hand. A plain radiograph of her right wrist is shown in the image. Which of the following bones is most likely fractured in this patient?

A 13-year-old girl presents to an orthopedic surgeon for evaluation of a spinal curvature that was discovered during a school screening. She has otherwise been healthy and does not take any medications. On presentation, she is found to have significant asymmetry of her back and is sent for a spine radiograph. The radiograph reveals a unilateral rib attached to the left transverse process of the C7 vertebrae. Abnormal expression of which of the following genes is most likely responsible for this finding?

A 35-year-old man comes to the physician because of a 3-month history of intermittent right lateral hip pain that radiates to the thigh. Climbing stairs and lying on his right side aggravates the pain. Examination shows tenderness to palpation over the upper lateral part of the right thigh. There is no swelling. When the patient is asked to abduct the right leg against resistance, tenderness is noted. An x-ray of the pelvis shows no abnormalities. Which of the following structures is the most likely source of this patient's pain?

Q10

A 25-year-old man presents with progressive weakness and urinary retention. MRI of the spine shows an intramedullary lesion from T10-T12 with expansion of the spinal cord and syrinx formation. The conus medullaris is identified at the L1-L2 level (normal: L1-L2). The filum terminale appears thickened at 3 mm. CSF flow study shows obstruction at the lesion site. Evaluate these radiologic landmarks and their relationships to determine the neurological level most likely affected.

Skeletal radiologic landmarks US Medical PG Practice Questions and MCQs

Question 1: A 23-year-old man complains of lower back pain that began approximately 6 months ago. He is unsure why he is experiencing this pain and notices that this pain is worse in the morning after waking up and improves with physical activity. Ibuprofen provides significant relief. He denies bowel and bladder incontinence or erectile dysfunction. Physical exam is notable for decreased chest expansion, decreased spinal range of motion, 5/5 strength in both lower extremities, 2+ patellar reflexes bilaterally, and an absence of saddle anesthesia. Which of the following is the most appropriate next test for this patient?

A. HLA-B27
B. Slit-lamp examination
C. MRI sacroiliac joint
D. Radiograph sacroiliac joint (Correct Answer)
E. ESR

Explanation: **Radiograph sacroiliac joint** - Plain **radiographs of the sacroiliac (SI) joints** are typically the **initial imaging modality** for suspected **ankylosing spondylitis** due to affordability and diagnostic value. - They can reveal characteristic changes such as **sacroiliitis (joint erosion, sclerosis, fusion)**, which are common in early-stage disease. *HLA-B27* - While a **positive HLA-B27** is associated with ankylosing spondylitis, it is **not diagnostic** on its own, as many HLA-B27 positive individuals never develop the disease. - Its use is more in **confirming suspicion** or in cases where imaging is equivocal, but it's not the primary diagnostic test. *Slit-lamp examination* - A slit-lamp examination is used to detect **uveitis**, which can be an **extra-articular manifestation** of ankylosing spondylitis. - However, it is not a primary diagnostic test for the condition itself, and its utility arises once the diagnosis is strongly considered or established. *MRI sacroiliac joint* - **MRI of the sacroiliac (SI) joints** is more sensitive than radiographs for detecting **early inflammatory changes** (e.g., bone marrow edema) that may not be visible on plain films. - However, given the duration of symptoms (6 months) and the characteristic inflammatory back pain, **radiographs are typically the first-line imaging** due to cost-effectiveness, reserving MRI for cases with normal radiographs but high clinical suspicion. *ESR* - **Erythrocyte sedimentation rate (ESR)** is a **non-specific marker of inflammation** and can be elevated in various inflammatory conditions, including ankylosing spondylitis. - It is not diagnostic for ankylosing spondylitis and cannot differentiate it from other inflammatory or infectious conditions.

Question 2: A 33-year-old man presents to his primary care physician with shoulder pain. He states that he can't remember a specific instance when the injury occurred. He is a weight lifter and competes in martial arts. The patient has no past medical history and is currently taking a multivitamin. Physical exam demonstrates pain with abduction of the patient's right shoulder and with external rotation of the right arm. There is subacromial tenderness with palpation. His left arm demonstrates 10/10 strength with abduction as compared to 4/10 strength with abduction of the right arm. Which of the following best confirms the underlying diagnosis?

A. Ultrasound
B. Radiography
C. MRI (Correct Answer)
D. CT
E. Physical exam and history

Explanation: ***MRI*** - An **MRI is the gold standard** for diagnosing soft tissue injuries of the shoulder, including **rotator cuff pathology**, which is highly suspected given the patient's symptoms (pain with abduction and external rotation, subacromial tenderness, and weakness). - It provides detailed imaging of tendons, ligaments, and cartilage, allowing for precise identification of **tears, inflammation, or impingement**. *Ultrasound* - While ultrasound can assess **rotator cuff integrity** and identify fluid collections, it is highly operator-dependent and may not provide the same level of detail as MRI for complex tears or associated pathologies. - It can be a good initial screening tool but might **underestimate the extent** of an injury compared to MRI. *Radiography* - **Radiography (X-rays)** primarily visualizes bone structures and would be useful for detecting fractures, dislocations, or significant degenerative joint disease. - It would **not directly visualize** the soft tissue injuries of the rotator cuff or other tendons that are likely causing this patient's symptoms. *CT* - **CT scans** provide excellent detail of bone structures and can identify subtle fractures, erosions, or bony impingement. - However, like X-rays, they are **less effective for visualizing soft tissues** like tendons and ligaments compared to MRI. *Physical exam and history* - The **physical exam and history** are crucial for narrowing down the differential diagnosis and guiding further imaging. - While strongly suggestive of a rotator cuff injury, they alone **cannot definitively confirm the extent or nature** of the underlying soft tissue pathology.

Question 3: A 50-year-old man presents with severe chest pain for a week. His pain increases with breathing and is localized to the right. He has tried over-the-counter medications at home, but they did not help. The patient has a 20-pack-year smoking history and currently smokes 2 packs of cigarettes daily, and he drinks 3 to 4 cans of beer daily before dinner. His temperature is 39.1°C (102.3°F), blood pressure is 127/85 mm Hg, pulse is 109/min, and respirations are 20/min. Respiratory examination shows dullness to percussion from the 7th rib inferiorly at the right midaxillary line, decreased vocal tactile fremitus, and diminished breath sounds in the same area. Chest radiograph is shown in the image. The patient is prepared for thoracocentesis. Which of the following locations would be the most appropriate for insertion of a chest tube?

A. Below the inferior border of the 7th rib in the midaxillary line
B. Above the superior border of the 8th rib in the midaxillary line (Correct Answer)
C. Above the superior border of the 5th rib in the midclavicular line
D. Below the inferior border of the 5th rib in the midaxillary line
E. Above the superior border of the 7th rib in the midclavicular line

Explanation: ***Above the superior border of the 8th rib in the midaxillary line*** - The patient presents with symptoms and signs suggestive of a **pleural effusion** (dullness to percussion, decreased fremitus, diminished breath sounds) and potentially an **empyema** given the fever and lung consolidation on the radiograph. - Thoracocentesis should be performed in the **midaxillary line** between the 6th and 9th ribs to avoid injuring the **diaphragm and abdominal organs**, which can rise as high as the 5th intercostal space during expiration. To prevent damage to the neurovascular bundle that runs along the inferior border of the ribs, the needle should be inserted just **above the superior border** of the rib below the chosen intercostal space. *Below the inferior border of the 7th rib in the midaxillary line* - Inserting below the inferior border of the 7th rib increases the risk of injuring the **neurovascular bundle** that runs along the inferior rib margin. - Such placement might also be too low, increasing the risk of penetrating the **diaphragm** or **abdominal organs**. This location would correspond to the 8th intercostal space, but the 'below inferior border' part is incorrect. *Above the superior border of the 5th rib in the midclavicular line* - The **midclavicular line** is typically used for needle decompression of a tension pneumothorax (2nd intercostal space) but is not the preferred site for thoracocentesis due to the risk of striking the lung parenchyma or internal mammary artery. - Even if considering a pneumothorax, the 5th intercostal space in the midclavicular line is not the standard site, and an effusion is indicated here. *Below the inferior border of the 5th rib in the midaxillary line* - Inserting below the inferior border of the 5th rib, similar to option A, risks injury to the **neurovascular bundle**. - While in the midaxillary line, the 5th rib might be too high for an effusion, and the technique of inserting below the inferior border is incorrect. *Above the superior border of the 7th rib in the midclavicular line* - The **midclavicular line** is generally avoided for thoracocentesis of effusions due to the risks mentioned previously and poor drainage if the effusion is posterior. - The 7th intercostal space in the midclavicular line is also a non-standard and less safe location for this procedure.

Question 4: A 22-year-old man is rushed to the emergency department after a motor vehicle accident. The patient states that he feels weakness and numbness in both of his legs. He also reports pain in his lower back. His airway, breathing, and circulation is intact, and he is conversational. Neurologic exam is significant for bilateral lower extremity flaccid paralysis and impaired pain and temperature sensation up to T10-T11 with normal vibration sense. A computerized tomography scan of the spine is performed which shows a vertebral burst fracture of the vertebral body at the level of T11. Which of the following findings is most likely present in this patient?

A. Intact vibration sense
B. Bowel incontinence (Correct Answer)
C. Flaccid paralysis at the level of the lesion
D. Spasticity below the lesion
E. Impaired proprioception sense

Explanation: ***Bowel incontinence*** - The presented symptoms of acute **bilateral lower extremity flaccid paralysis**, **impaired pain and temperature sensation**, and a T11 **vertebral burst fracture** are highly indicative of **anterior cord syndrome**. - **Anterior cord syndrome** characteristically involves damage to the **anterior two-thirds of the spinal cord**, affecting the **corticospinal tracts** (motor control), **spinothalamic tracts** (pain and temperature sensation), and the **autonomic fibers** that control bladder and bowel function, leading to **bowel and bladder dysfunction**. *Intact vibration sense* - The sensation of **vibration** and **proprioception** is carried by the **dorsal columns** (posterior part of the spinal cord), which are typically **spared** in **anterior cord syndrome**. - Therefore, **intact vibration sense** is an expected finding, but the question asks for the **most likely finding** that represents a significant complication of the syndrome. *Flaccid paralysis at the level of the lesion* - While **flaccid paralysis** is present in the lower extremities, it occurs **below the level of the lesion** due to damage to the descending motor tracts (corticospinal tracts). - Flaccid paralysis *at* the level of the lesion would typically involve damage to the **lower motor neurons** at that specific segment, which is not the primary feature described for a burst fracture causing **anterior cord syndrome**. *Spasticity below the lesion* - **Spasticity** typically develops much **later** in spinal cord injuries, after the initial phase of **spinal shock** resolves (usually weeks to months). - In the acute phase following a significant spinal cord injury, **flaccid paralysis** is the more common finding below the lesion, reflecting spinal shock. *Impaired proprioception sense* - Similar to vibration sense, **proprioception** is primarily mediated by the **dorsal columns**, which are generally **spared** in **anterior cord syndrome**. - Therefore, **proprioception** would likely be **intact**, not impaired, in this specific type of spinal cord injury.

Question 5: A 69-year-old woman presents with pain in her hip and groin. She states that the pain is present in the morning, and by the end of the day it is nearly unbearable. Her past medical history is notable for a treated episode of acute renal failure, diabetes mellitus, obesity, and hypertension. Her current medications include losartan, metformin, insulin, and ibuprofen. The patient recently started taking high doses of vitamin D as she believes that it could help her symptoms. She also states that she recently fell off the treadmill while exercising at the gym. On physical exam you note an obese woman. There is pain, decreased range of motion, and crepitus on physical exam of her right hip. The patient points to the areas that cause her pain stating that it is mostly over the groin. The patient's skin turgor reveals tenting. Radiography is ordered. Which of the following is most likely to be found on radiography?

A. Loss of joint space and osteophytes (Correct Answer)
B. Posterior displacement of the femoral head
C. Hyperdense foci in the ureters
D. Femoral neck fracture
E. Normal radiography

Explanation: ***Loss of joint space and osteophytes*** - The patient's presentation with **hip and groin pain worsened by activity**, improved with rest, and associated with **crepitus** and **decreased range of motion**, is highly suggestive of **osteoarthritis**. - **Osteoarthritis** is characterized radiographically by **loss of joint space**, **osteophytes** (bone spurs), subchondral sclerosis, and subchondral cysts. *Posterior displacement of the femoral head* - This finding is characteristic of a **posterior hip dislocation**, which usually presents with severe pain and an inability to bear weight after a significant traumatic event. - While the patient fell, her symptoms are chronic and progressive, and she has signs of arthritis rather than acute dislocation. *Hyperdense foci in the ureters* - These would indicate **kidney stones**, which typically present with acute, severe flank pain radiating to the groin, and hematuria. - The patient's symptoms are chronic and localized to the hip joint, making kidney stones an unlikely cause of her primary complaint. *Femoral neck fracture* - A **femoral neck fracture** would cause acute, severe hip pain, inability to bear weight, and often external rotation and shortening of the leg, usually following a fall. - Although she fell, her chronic, activity-related pain and crepitus are more indicative of a degenerative process. *Normal radiography* - Given the patient's age, chronic and worsening hip pain, physical exam findings of crepitus and decreased range of motion, and risk factors like obesity, it is highly improbable that her hip X-rays would be normal. - These symptoms are classic for **osteoarthritis**, which shows distinct radiographic changes.

Question 6: A 45-year-old man presents for a follow-up visit as part of his immigration requirements into the United States. Earlier this week, he was administered the Mantoux tuberculin skin test (TST). Today’s reading, 3 days after being administered the test, he shows an induration of 10 mm. Given his recent immigration from a country with a high prevalence of tuberculosis, he is requested to obtain a radiograph of the chest, which is shown in the image. Which of the following is true regarding this patient’s chest radiograph (CXR)?

A. Posterior ribs 9 and 10 are visible only in an expiratory film.
B. The right lower boundary of the mediastinal silhouette belongs to the right ventricle.
C. If the spinous process is not in-between the two clavicular heads, the image is repeated. (Correct Answer)
D. The film is taken in a supine position.
E. The view is anteroposterior (AP).

Explanation: ***If the spinous process is not in-between the two clavicular heads, the image is repeated.*** - Proper patient positioning is crucial for an accurate chest X-ray; **rotation of the patient** can distort the appearance of the heart and lungs, simulating pathology or obscuring real findings. - Symmetrical positioning, indicated by the **spinous process being equidistant from the medial ends of the clavicles**, ensures an ideal posteroanterior (PA) view for interpretation. *Posterior ribs 9 and 10 are visible only in an expiratory film.* - In a properly **inspired chest X-ray**, at least 9 or 10 posterior ribs (or 5-6 anterior ribs) should be visible above the diaphragm. - If fewer ribs are visible on a standard PA film, it indicates a **poor inspiratory effort**, which can compress lung fields and mimic pathology. *The right lower boundary of the mediastinal silhouette belongs to the right ventricle.* - The **right lower boundary of the mediastinal silhouette** is formed by the right atrium, not the right ventricle. - The right ventricle forms part of the **anterior cardiac border** and is typically not seen as a distinct border on a standard PA chest X-ray. *The film is taken in a supine position.* - The presence of the **gastric bubble visible below the left hemidiaphragm** confirms an upright position, as gas rises in the stomach. - A supine film would typically result in a **magnified cardiac silhouette** and less prominent gastric air. *The view is anteroposterior (AP).* - In an AP view, the **medial ends of the clavicles overlay the lung apices**, and the scapulae are often within the lung fields; this image shows the scapulae largely clear of the lung fields, consistent with a PA view. - AP films also tend to **magnify the heart shadow** due to the divergent X-ray beam, which is not evident here.

Question 7: A 33-year-old woman presents to the emergency department with pain in her right wrist. She says she was walking on the sidewalk a few hours ago when she suddenly slipped and landed forcefully on her outstretched right hand with her palm facing down. The patient is afebrile, and vital signs are within normal limits. Physical examination of her right wrist shows mild edema and tenderness on the lateral side of the right hand with a decreased range of motion. Sensation is intact. The patient is able to make a fist and OK sign with her right hand. A plain radiograph of her right wrist is shown in the image. Which of the following bones is most likely fractured in this patient?

A. Bone labeled 'A'
B. Bone labeled 'D' (Correct Answer)
C. Bone labeled 'C'
D. Bone labeled 'E'
E. Bone labeled 'B'

Explanation: ***Bone labeled 'D'*** - The clinical presentation of a fall on an **outstretched hand (FOOSH)** with pain on the **lateral aspect** of the wrist suggests a **scaphoid fracture**. - Bone 'D' is the **scaphoid bone**, which is commonly fractured in this mechanism due to its position and poor blood supply, making it prone to **avascular necrosis** if untreated. *Bone labeled 'A'* - Bone 'A' is the **ulna**, which is less commonly fractured due to FOOSH injuries unless there is a direct impact or significant rotational force. - While it articulates with the wrist, a fracture of the ulna would typically present with pain more medially and potentially forearm instability. *Bone labeled 'C'* - Bone 'C' is the first **metacarpal**, part of the thumb, which is distal to the wrist joint. - A fracture here would cause pain more specifically localised to the thumb base rather than the general wrist area as described. *Bone labeled 'E'* - Bone 'E' is the **hamate bone**, located in the distal carpal row. - Fractures of the hamate are less common than scaphoid fractures via FOOSH and are often associated with direct impact (e.g., from a golf club) or forceful gripping. *Bone labeled 'B'* - Bone 'B' represents the **radius**, specifically its distal portion. While a **Colles fracture** of the distal radius is common with FOOSH, the tenderness being on the "lateral side of the right hand" specifically points away from a general distal radius fracture and more towards the carpal bones, particularly the scaphoid. - A Colles fracture often results in a **"dinner fork" deformity**, which is not mentioned in the presentation, and tenderness would be more widespread over the distal forearm.

Question 8: A 13-year-old girl presents to an orthopedic surgeon for evaluation of a spinal curvature that was discovered during a school screening. She has otherwise been healthy and does not take any medications. On presentation, she is found to have significant asymmetry of her back and is sent for a spine radiograph. The radiograph reveals a unilateral rib attached to the left transverse process of the C7 vertebrae. Abnormal expression of which of the following genes is most likely responsible for this finding?

A. WNT7
B. FGF
C. Homeobox (Correct Answer)
D. PAX
E. Sonic hedgehog

Explanation: ***Homeobox*** - **Homeobox genes (HOX genes)** play a crucial role in specifying the identity of vertebral segments along the **craniocaudal axis** during embryonic development. - An abnormal expression of these genes can lead to **skeletal malformations**, such as the formation of a **cervical rib**, by altering the segmental identity of the C7 vertebra. *WNT7* - **WNT7 genes** are involved in limb patterning and have a role in the formation of the **dorsoventral axis** of the limb and kidney development. - They are not primarily associated with vertebral segmentation or the formation of cervical ribs. *FGF* - **Fibroblast growth factor (FGF) genes** are essential for various processes, including limb development, neurogenesis, and angiogenesis. - While they are involved in numerous developmental pathways, they are not the primary genes responsible for specifying vertebral identity and thus cervical rib formation. *PAX* - **PAX genes** are a family of transcription factors critical for organ development, especially of the eye, brain, and kidney. - While important for development, they are not directly implicated in the specification of vertebral segments or the pathogenesis of cervical ribs. *Sonic hedgehog* - **Sonic hedgehog (SHH)** signaling is a key pathway in embryonic development, particularly for pattern formation in the neural tube, limbs, and facial structures. - While crucial for body axis development and segmentation, **HOX genes** have a more direct role in determining the specific identity of vertebral segments and causing cervical ribs.

Question 9: A 35-year-old man comes to the physician because of a 3-month history of intermittent right lateral hip pain that radiates to the thigh. Climbing stairs and lying on his right side aggravates the pain. Examination shows tenderness to palpation over the upper lateral part of the right thigh. There is no swelling. When the patient is asked to abduct the right leg against resistance, tenderness is noted. An x-ray of the pelvis shows no abnormalities. Which of the following structures is the most likely source of this patient's pain?

A. Femoral head
B. Greater trochanter (Correct Answer)
C. Iliotibial band
D. Acetabulum
E. Lateral femoral cutaneous nerve

Explanation: ***Greater trochanter*** - The patient's symptoms of **intermittent right lateral hip pain** radiating to the thigh, aggravated by climbing stairs and lying on the affected side, and tenderness over the **upper lateral part of the right thigh** are classic signs of **trochanteric bursitis**. - Pain with **resisted abduction** further points to inflammation of the **gluteus medius** or its associated bursa at the greater trochanter. *Femoral head* - Pain originating from the **femoral head** typically presents as deep, generalized groin or hip joint pain, often exacerbated by weight-bearing activities, and may be associated with limited range of motion in multiple planes. - An **x-ray showing no abnormalities** makes femoral head issues like avascular necrosis or significant arthritis less likely. *Iliotibial band* - **Iliotibial band (ITB) syndrome** usually causes pain along the **lateral aspect of the knee**, particularly in runners or cyclists, due to friction over the lateral femoral epicondyle. - While the ITB traverses the lateral thigh, the primary point of tenderness and mechanism of pain in this case (tenderness over the upper lateral thigh, pain with resisted abduction) is not typical for ITB syndrome affecting the knee. *Acetabulum* - Pain from the **acetabulum** would generally be deep within the hip joint, similar to femoral head issues, and often accompanied by a **limited range of motion** or clicking/locking sensations, and would be associated with intra-articular pathology. - An **unremarkable X-ray** and the specific finding of **tenderness over the lateral thigh** make acetabular pathology less likely. *Lateral femoral cutaneous nerve* - Entrapment of the **lateral femoral cutaneous nerve** (meralgia paresthetica) typically causes **numbness, burning, or tingling** on the anterolateral thigh, not primarily sharp, intermittent pain aggravated by movement and palpation in the manner described. - While pain can be present, the absence of **paresthesias** and the mechanical nature of the pain (aggravated by resisted abduction) make nerve entrapment less probable.

Question 10: A 25-year-old man presents with progressive weakness and urinary retention. MRI of the spine shows an intramedullary lesion from T10-T12 with expansion of the spinal cord and syrinx formation. The conus medullaris is identified at the L1-L2 level (normal: L1-L2). The filum terminale appears thickened at 3 mm. CSF flow study shows obstruction at the lesion site. Evaluate these radiologic landmarks and their relationships to determine the neurological level most likely affected.

A. Cauda equina only, sparing upper motor neurons
B. Conus medullaris with mixed upper and lower motor neuron signs
C. Thoracic cord with pure upper motor neuron signs below T10
D. Epiconus (T12-L1) with distal lower extremity and sphincter dysfunction (Correct Answer)
E. Lower thoracic nerve roots with radicular pain pattern only

Explanation: ***Epiconus (T12-L1) with distal lower extremity and sphincter dysfunction*** - The **epiconus** encompasses spinal segments **L4-S2**, which anatomically correspond to the vertebral levels **T12-L1**; a lesion here characteristically causes **bladder/bowel dysfunction** and weakness. - This location accounts for the **urinary retention** and progressive weakness while sparing the higher thoracic functions, fitting the intramedullary expansion seen at the lower thoracic-lumbar transition. *Cauda equina only, sparing upper motor neurons* - A **cauda equina** lesion involves the **nerve roots** below the level of the conus (L2) and presents with **purely lower motor neuron (LMN)** signs. - The intramedullary nature of the lesion at **T10-T12** indicates involvement of the spinal cord itself, which would typically involve **upper motor neuron (UMN)** features or a mixed picture. *Conus medullaris with mixed upper and lower motor neuron signs* - The **conus medullaris** corresponds to segments **S3-Co1** and is located at the vertebral level of **L1-L2**, which is distal to the primary lesion core reported at T10. - Conus lesions typically present with **early autonomic dysfunction** and symmetric saddle anesthesia, but the lesion described extends higher into the **epiconus** region. *Thoracic cord with pure upper motor neuron signs below T10* - A lesion at the **mid-thoracic cord** (T10-T12) would primarily produce **spasticity** and hyperreflexia typical of **UMN syndrome** in the lower extremities. - However, because this specific region houses the lower lumbar and upper sacral segments (the **epiconus**), it frequently yields a complex focal clinical picture involving specific root-level deficits. *Lower thoracic nerve roots with radicular pain pattern only* - **Radicular pain** results from compression of exiting **nerve roots**, whereas an **intramedullary lesion** like the one described involves the central cord parenchyma. - The presence of **urinary retention** and a **syrinx** indicates deep spinal cord involvement and syrinx-related neurological deficits, not mere peripheral root irritation.

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