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 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 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?

Flaccid paralysis at the level of the lesion

A 80-year-old man is brought to the emergency department with complaints that he "can't control his left leg". His symptoms started a few hours ago. He was outside taking a walk with his wife when suddenly his leg shot out and kicked her. His past medical history is notable for diabetes, hypertension, and a myocardial infarction 5 years ago. He smokes 1-2 cigarettes/day. He does not use alcohol or illicit drugs. On exam, the patient has intermittent wide, flinging movements that affect his proximal left arm and left leg. Which of the following parts of his brain is most likely damaged?

Ventral posterior thalamic nucleus

A 74-year-old male is brought to the emergency department 1 hour after he fell from the top of the staircase at home. He reports pain in his neck as well as weakness of his upper extremities. He is alert and immobilized in a cervical collar. He has hypertension treated with hydrochlorothiazide. His pulse is 90/min and regular, respirations are 18/min, and blood pressure is 140/70 mmHg. Examination shows bruising and midline cervical tenderness. Neurologic examination shows diminished strength and sensation to pain and temperature in the upper extremities, particularly in the hands. Upper extremity deep tendon reflexes are absent. Strength, sensation, and reflexes in the lower extremities are intact. Anal sensation and tone are present. Babinski's sign is absent bilaterally. Which of the following is most likely to confirm the cause of this patient's neurologic examination findings?

MRI of the cervical spine without contrast

CT of the cervical spine with contrast

A 23-year-old man presents to the emergency room following a stab wound to the back. He was in a bar when he got into an argument with another man who proceeded to stab him slightly right of the midline of his back. He is otherwise healthy and does not take any medications. He has one previous admission to the hospital for a stab wound to the leg from another bar fight 2 years ago. His temperature is 99°F (37.2°C), blood pressure is 115/80 mmHg, pulse is 100/min, and pulse oximetry is 99% on room air. Cardiopulmonary and abdominal exams are unremarkable; however, he has an abnormal neurologic exam. If this wound entered his spinal cord but did not cross the midline, which of the following would most likely be seen in this patient?

Ipsilateral flaccid paralysis at the level of the lesion

Contralateral spasticity below the level of the lesion

Ipsilateral loss of pain and temperature sensation below the lesion

Contralateral loss of tactile, vibration, and proprioception below the lesion

Contralateral loss of sensation at the level of the lesion

Spinal cord injury levels and their effects — USMLE Lesson

Corticospinal Tracts - The Brain's Highway

Primary motor pathway for voluntary movement, originating from the cerebral cortex.
UMN vs. LMN: Connects upper motor neurons (UMN) in the brain to lower motor neurons (LMN) in the spinal cord.

Corticospinal Tract Pathway with Decussation

⭐ Clinical Pearl: Lesions above the pyramidal decussation (e.g., stroke) cause contralateral motor deficits. Lesions below the decussation (e.g., Brown-Séquard syndrome) cause ipsilateral paralysis.

Spinal Cord Map - Body's Wiring Diagram

Dermatome and Myotome Map

Cervical: Controls diaphragm, arms, hands.
- C3-C5: Phrenic nerve (diaphragm). Injury above C3 necessitates ventilation.
- C5: Biceps (flexion); C7: Triceps (extension).
Thoracic: Trunk muscles, intercostals.
- T4: Nipple line sensory level.
- T10: Umbilicus sensory level.
Lumbar: Leg muscles.
- L4: Patellar reflex ("kick the door").
Sacral: Bowel, bladder, sexual function.
- 📌 S2, 3, 4: Keep the "3 P's" (penis, pee, poop) off the floor.

⭐ Sacral sparing-perianal sensation preservation-is a key prognostic indicator in acute spinal cord injury, signifying an incomplete lesion with potential for recovery.

Spinal Cord Syndromes - When the Signal Drops

Spinal Cord Tracts & Injury Syndromes

Anterior Cord Syndrome
- Mechanism: Occlusion of anterior spinal artery.
- Presentation: Complete motor paralysis and loss of pain/temperature sensation below the lesion.
- Spared: Dorsal column function (proprioception, vibration).
Central Cord Syndrome
- Mechanism: Hyperextension injury in cervical spine, common in elderly.
- Presentation: Motor impairment, arms more affected than legs. Sensory loss variable.
Brown-Séquard Syndrome
- Mechanism: Hemisection of the cord (e.g., penetrating trauma).
- Presentation (at and below lesion level):
  - Ipsilateral: UMN paralysis, loss of proprioception/vibration.
  - Contralateral: Loss of pain/temperature (spinothalamic tract decussates).
- 📌 Mnemonic: "The same side feels the vibe but can't move; the other side feels the pain but can move."

⭐ Exam Favorite: Central Cord Syndrome classically presents as a "man in a barrel" deficit (bilateral arm weakness) after a fall in an elderly patient with pre-existing cervical spondylosis.

Injury Levels & Effects - Functional Fallout

C1-C4: Quadriplegia, ventilator-dependent (phrenic n. C3-5).
- 📌 "C3, 4, 5 keep the diaphragm alive."
C5: Quadriplegia, elbow flexion intact. No wrist/hand control.
C6: Wrist extension preserved, enabling tenodesis grasp for self-feeding.
C7: Elbow extension (triceps) allows independent transfers. 📌 "C7 to heaven."
T1-T12: Paraplegia, trunk control varies. Full arm function.
L-Spine: Paraplegia, variable leg function.
S2-S4: Bowel, bladder, sexual dysfunction.
- 📌 "S2, 3, 4 keep the penis off the floor."

⭐ Sacral Sparing: Perianal sensation or voluntary anal/toe flexion indicates an incomplete lesion, the key prognostic factor for motor recovery.

High‑Yield Points - ⚡ Biggest Takeaways

Lesions above C3-C5 risk respiratory arrest from phrenic nerve disruption.

Injury produces LMN signs (flaccid paralysis) at the lesion level and UMN signs (spasticity) below.

Brown-Séquard syndrome: Ipsilateral motor/proprioception loss; contralateral pain/temperature loss.

Anterior cord syndrome spares dorsal columns, preserving proprioception and vibration.

Central cord syndrome features greater weakness in the upper limbs than lower limbs.

Autonomic dysreflexia (injury at T6 or above) causes severe, episodic hypertension.

Sacral sparing indicates an incomplete lesion and better prognosis.

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