A patient with a known spinal cord ependymoma presents to his neurologist for a check up. He complains that he has had difficulty walking, which he attributes to left leg weakness. On exam, he is noted to have 1/5 strength in his left lower extremity, as well as decreased vibration and position sensation in the left lower extremity and decreased pain and temperature sensation in the right lower extremity. Which of the following spinal cord lesions is most consistent with his presentation?

Left-sided Brown-Sequard (hemisection)

Right-sided Brown-Sequard (hemisection)

A 61-year-old man is found dead in his home after his neighbors became concerned when they did not see him for several days. The man was described as a "recluse" who lived alone and mostly kept to himself. Medical records reveal that he had not seen a physician in over a decade. He had a known history of vascular disease including hypertension, hyperlipidemia, and diabetes mellitus. He did not take any medications for these conditions. An autopsy is performed to identify the cause of death. Although it is determined that the patient suffered from a massive cerebrovascular accident as the cause of death, an incidental finding of a tumor arising from the spinal cord meninges is noted. The tumor significantly compresses the left anterolateral lower thoracic spinal cord. The right side of the spinal cord and the posterior spinal cord appear normal. Which of the following would most likely be impaired due to this lesion?

Pain sensation from the right side of the body

Proprioceptive sensation from the left side of the body

Temperature sensation from the left side of the body

Pressure sensation from the left side of the body

Vibratory sensation from the right side of the body

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

Ascending sensory pathways in brainstem for USMLE Step 3: High-Yield Anatomy Lessons

Sensory Pathways Overview - The Brain's Info Highways

Dorsal Column-Medial Lemniscus (DCML): Carries fine touch, vibration, proprioception.
Spinothalamic Tract (STT): Carries pain, temperature, crude touch.

General 3-neuron pathway structure:

Ascending Sensory Pathways in Brainstem

⭐ All sensory information is relayed through the thalamus before reaching the cortex, with the notable exception of olfaction.

Dorsal Column-Medial Lemniscus - The VIP Touch Club

📌 Vibration, Intelligent touch (e.g., 2-point discrimination), Proprioception.

Carries sensory information for:

Fine Touch & Stereognosis: Identifying objects by feel.
Conscious Proprioception: Joint and limb position sense.
Vibration: Sensed by Pacinian corpuscles.

Ascending Sensory Pathways in Brainstem

⭐ Lesions in the spinal cord cause ipsilateral loss of vibration and proprioception below the lesion level. Lesions above the medulla cause contralateral loss.

Anterolateral System - Pain & Temp Express

Function: Transmits pain, temperature, and crude touch.
Fibers: Aδ (fast, sharp pain) & C-fibers (slow, dull pain).
Tracts:
- Lateral spinothalamic: Pain & temperature.
- Anterior spinothalamic: Crude touch & pressure.

Spinal Cord Tracts Cross-Section

⭐ Syringomyelia: A fluid-filled cavity (syrinx) in the spinal cord damages the anterior white commissure, causing bilateral loss of pain and temperature in a "cape-like" distribution across the shoulders.

📌 Somatotopy: Sacral tracts are lateral, cervical are medial.

Trigeminal Sensory Pathways - Just for the Face

Ascending Sensory Pathways in Brainstem

Pain, Temperature, & Crude Touch: Synapses in the Spinal Trigeminal Nucleus.
Fine Touch, Vibration, & Proprioception: Synapses in the Principal (Chief) Sensory Nucleus.
- Both pathways decussate, ascending via the trigeminal lemniscus to the thalamus.

⭐ The Ventral Posteromedial (VPM) nucleus is the thalamic relay for all face sensation, while the VPL nucleus serves the body. 📌 Makeup on the Face (VPM).

Clinical Correlations - Pathway Pile-ups

Brainstem lesions often damage adjacent tracts, causing complex "pathway pile-up" syndromes.
Key vulnerable tracts: Medial Lemniscus (ML), Spinothalamic Tract (STT), and Trigeminal sensory nuclei.
This proximity results in "crossed findings": ipsilateral facial sensory loss with contralateral body sensory loss.
Example: Lateral Medullary (Wallenberg) Syndrome damages the STT and spinal trigeminal nucleus.

⭐ "Crossed findings"-ipsilateral face and contralateral body deficits-are a classic localizing sign for brainstem lesions, distinguishing them from cortical strokes.

High‑Yield Points - ⚡ Biggest Takeaways

The Dorsal Column-Medial Lemniscus (DCML) pathway, for fine touch, vibration, and proprioception, decussates in the caudal medulla.

The Anterolateral System (Spinothalamic Tract), for pain and temperature, decussates in the spinal cord.

All sensory information for the body projects to the VPL nucleus of the thalamus; facial sensation projects to the VPM nucleus.

The lateral lemniscus is the primary auditory pathway in the brainstem.

The Medial Longitudinal Fasciculus (MLF) is key for coordinating eye movements.

Continue reading on Oncourse

CONTINUE READING — FREE

or get the app

App Store|Google Play