A 35-year-old man who suffered a motor vehicle accident 3 months ago presents to the office for a neurological evaluation. He has no significant past medical history and takes no current medications. He has a family history of coronary artery disease in his father and Alzheimer’s disease in his mother. On physical examination, his blood pressure is 110/60 mm Hg, the pulse is 85/min, the temperature is 37.0°C (98.6°F), and the respiratory rate is 20/min. Neurological examination is suggestive of a lesion in the anterior spinal artery that affects the anterior two-thirds of the spinal cord, which is later confirmed with angiography. Which of the following exam findings would have suggested this diagnosis?

Loss of vibratory sense below the level of the lesion

Loss of pain and temperature sensation above the level of the lesion

Negative plantar extensor response in his lower limbs

Flaccid paralysis on the right side

A 57-year-old woman presents to an outpatient clinic with lower extremity weakness and lower back pain. The patient says that her symptoms began 2 weeks ago when she was working in her garden and have progressively worsened to the extent she currently is unable to walk on her own. She describes the pain as sharp, severe and descending bilaterally from her lower back to her lateral ankles along the posterior surface of her thighs and legs. She also states that she has had several episodes of urinary incontinence for the past couple of days. The patient denies having any similar pain or incontinence in the past. No other significant past medical history. Current medications are alendronate 5 mg orally daily and a daily multivitamin. Her temperature is 37.0℃ (98.6℉), the blood pressure is 110/70 mm Hg, the pulse is 72/min, the respiratory rate is 15/min, and oxygen saturation is 99% on room air. On physical examination, the patient appears to be in significant distress. Strength is ⅗ in her thighs bilaterally and ⅖ in the legs bilaterally left greater than right. Muscle tone is decreased in the lower extremities. The patellar reflex is 1+ bilaterally and plantar reflex is 0+ bilaterally. Fine touch and pain and temperature sensation are decreased in the lower extremities bilaterally, left greater than right. Saddle anesthesia is present. Which of the following is the next, best step in the management of this patient?

Immediate transfer to the emergency department for management

Outpatient management with a 3-day course of meloxicam and tolperisone and reassess

Recommend non-emergent inpatient spinal manipulation program

Outpatient management with a 3-day course of diclofenac and gabapentin and reassess

Outpatient management with 3 days of strict bed rest and reassess

A 38-year-old man comes to the physician for a follow-up examination. He has quadriparesis as a result of a burst fracture of the cervical spine that occurred after a fall from his roof 1 month ago. He has urinary and bowel incontinence. He appears malnourished. His temperature is 37.1°C (98.8°F), pulse is 88/min, and blood pressure is 104/60 mm Hg. Examination shows spasticity in all extremities. Muscle strength is decreased in proximal and distal muscle groups bilaterally. Deep tendon reflexes are 4+ bilaterally. Plantar reflex shows extensor response bilaterally. Sensation to pinprick and temperature is absent below the neck. Sensation to vibration, position, and light touch is normal bilaterally. Rectal tone is decreased. There is a 1-cm area of erythema over the sacrum. Which of the following is the most likely cause of this patient's symptoms?

Damage to the anterior spinal artery

Hemi-transection of the spinal cord

Cavitation within the spinal cord

Injury to gray matter of the spinal cord

Occlusion of the posterior spinal artery

A 21-year-old man was involved in a motor vehicle accident and died. At autopsy, the patient demonstrated abnormally increased mobility at the neck. A section of cervical spinal cord at C6 was removed and processed into slides. Which of the following gross anatomic features is most likely true of this spinal cord level?

Cuneate and gracilis fasciculi are present

Absence of gray matter enlargement

Involvement with parasympathetic nervous system

A 69-year-old male presents to the emergency room with back pain. He has a history of personality disorder and metastatic prostate cancer and was not a candidate for surgical resection. He began chemotherapy but discontinued due to unremitting nausea. He denies any bowel or bladder incontinence. He has never had pain like this before and is demanding morphine. The nurse administers IV morphine and he feels more comfortable. Vital signs are stable. On physical examination you note tenderness to palpation along the lower spine, weakness in the bilateral lower extremities, left greater than right. Neurological examination is also notable for hyporeflexia in the knee and ankle jerks bilaterally. You conduct a rectal examination, which reveals saddle anesthesia. Regarding this patient, what is the most likely diagnosis and the appropriate next step in management?

The most likely diagnosis is cauda equina syndrome and steroids should be started prior to MRI

The most likely diagnosis is cauda equina syndrome and the patient should be rushed to radiation

The most likely diagnosis is conus medullaris syndrome and steroids should be started prior to MRI

The most likely diagnosis is conus medullaris syndrome and steroids should be started after MRI

The most likely diagnosis is cauda equina syndrome and steroids should be started after MRI

Spinal surgery fundamentals for USMLE Step 3: High-Yield Surgery Lessons

🦴 Anatomy - The Bony Framework

Vertebral Column: 33 vertebrae total.
- Cervical: 7 (C1-C7)
- Thoracic: 12 (T1-T12)
- Lumbar: 5 (L1-L5)
- Sacral: 5 (fused into sacrum)
- Coccygeal: 4 (fused into coccyx)
Typical Vertebra Components:
- Anterior: Vertebral Body (weight-bearing).
- Posterior Arch: Pedicles, Laminae, Spinous Process, Transverse Processes, and Articular Facets (form zygapophyseal joints).
Atypical Vertebrae:
- C1 (Atlas): Ring-like, no body.
- C2 (Axis): Has dens (odontoid process) for pivot rotation.

Typical vertebra anatomy: superior and lateral views

⭐ Jefferson Fracture: A burst fracture of the C1 ring from axial loading (e.g., diving injury). On open-mouth X-ray, look for lateral displacement of C1's lateral masses relative to C2.

🧠 Anatomy - Neurological & Vascular Supply

Spinal Cord: Ends as the conus medullaris at the L1-L2 vertebral level in adults. Nerve roots below this form the cauda equina.
Key Nerve Roots (Myotomes):
- C5: Deltoid (shoulder abduction)
- C7: Triceps (elbow extension)
- L4: Quadriceps (knee extension)
- L5: Tibialis anterior (foot dorsiflexion)
- S1: Gastrocnemius (foot plantarflexion)
Arterial Supply:
- Anterior Spinal Artery (ASA): Single artery supplying the anterior 2/3 of the cord (motor pathways).
- Posterior Spinal Arteries (PSAs): Paired arteries supplying the posterior 1/3 (sensory pathways).

⭐ The Artery of Adamkiewicz is the largest segmental artery, crucial for lower cord perfusion. Ischemia leads to Anterior Cord Syndrome-bilateral paralysis and loss of pain/temp, with preserved dorsal column function.

Spinal cord arterial supply territories

🔪 Surgical Approaches & Corridors

Goal: Safely access spinal pathology while minimizing iatrogenic injury. The corridor choice is dictated by pathology location (e.g., anterior disc vs. posterior lamina), spinal level, and surgeon preference.

Approach	Corridor & Key Structures	Common Uses	⚠️ Key Risks
Anterior	Retroperitoneal (lumbar); between carotid/trachea (cervical)	ACDF, ALIF, Corpectomy	Great vessels, recurrent laryngeal nerve (RLN), esophagus
Posterior	Midline, splitting paraspinal muscles	Laminectomy, Discectomy, Pedicle screw fixation	Dural tear, nerve root injury, post-op muscle pain
Lateral	Transpsoas (XLIF), retroperitoneal	Lateral interbody fusion (L1-L5)	Lumbar plexus injury, psoas hematoma/weakness

🩺 Clinical - Indications & Pathologies

Degenerative Disease (Most Common):
- Herniated Nucleus Pulposus (HNP): For radiculopathy or myelopathy refractory to conservative care.
- Spinal Stenosis: Central or foraminal, causing neurogenic claudication.
- Spondylolisthesis: Instability with back pain or radiculopathy.
Trauma:
- Unstable fractures (e.g., Burst, Chance) or ligamentous injury.
- Spinal Cord Injury (SCI) with persistent cord compression.
Oncology:
- Metastatic disease (📌 BLT w/ Kosher Pickle) or primary tumors causing instability or neurologic deficit.
Infection:
- Spinal Epidural Abscess, Vertebral Osteomyelitis/Discitis with instability or neurologic compromise.

⭐ Cauda Equina Syndrome (saddle anesthesia, bowel/bladder dysfunction, bilateral leg weakness) is a neurosurgical emergency requiring immediate decompression.

MRI Lumbar Spine: L4-L5 Disc Herniation & Nerve Compression

⚠️ Complications - Post-Op Pitfalls

Infection: Superficial or deep (discitis, epidural abscess). ↑ risk with diabetes, obesity.
Dural Tear / CSF Leak: Presents as postural headache. Test fluid for β-2 transferrin.
Hardware Failure: Malposition, loosening, or fracture of screws/rods.
Neurologic Deficit: New or worsening weakness/numbness from nerve root injury or hematoma.
Epidural Hematoma: Surgical emergency causing rapid neuro decline.

⭐ Post-op epidural hematoma causing cauda equina syndrome (saddle anesthesia, bowel/bladder dysfunction) requires immediate surgical decompression.

⚡ Biggest Takeaways

Cauda Equina Syndrome is a surgical emergency: presents with saddle anesthesia, bowel/bladder dysfunction, and requires urgent decompression.

For suspected spinal cord compression, give IV dexamethasone immediately, followed by an emergent MRI.

Radiculopathy (nerve root) causes LMN signs in a dermatome; Myelopathy (cord) causes UMN signs below the lesion.

Spinal stenosis causes neurogenic claudication, which is relieved by spinal flexion (e.g., leaning forward).

Most common disc herniations are L4-L5 and L5-S1.

Continue reading on Oncourse

CONTINUE READING — FREE

or get the app

App Store|Google Play