In Brown-Sequard syndrome, if a person has right side hemisection, which side of anterolateral spinothalamic pathway is affected? According to Sillivan anterolateral spinothalamic pathway enters from dorsal root and crosses over immediately and ascends. If right side is cut then nerve fibers from right dorsal root is cut as well as right anterolateral spinothalamic pathway is cut. Are both sides anterolateral spinothalamic tracts affected?

Brown-Séquard syndrome is an incomplete spinal cord lesion. Patients with Brown-Séquard syndrome (say, for instance, resulting from injury to the right side of the spinal cord) will suffer from ipsilateral (right sided) upper motor neuron paralysis and loss of proprioception, as well as contralateral (left sided) loss of pain and temperature sensation. A zone of partial preservation or segmental ipsilateral lower motor neuron weakness and analgesia may be noted.

No, only one side of the anterolateral spinothalamic tract is affected which gives rise to the distinct neurological manifestations that occur on both sides of the body. If both sides were affected, then we would have a complete spinal cord injury. Spinal cord anatomy accounts for the clinical presentation of Brown-Séquard syndrome. The motor fibers of the corticospinal tracts cross at the junction of the medulla and spinal cord. The ascending dorsal column, carrying the sensations of vibration and position, runs ipsilateral to the roots of entry and crosses above the spinal cord in the medulla. The spinothalamic tracts convey sensations of pain, temperature, and crude touch from the contralateral side of the body. At the site of spinal cord injury, nerve roots and/or anterior horn cells also may be affected.

The fibers of the spinothalamic tract decussate at the level of the spinal cord. Therefore, a hemi-section lesion to the spinal cord will demonstrate loss of pain, temperature, and crude touch sensations on the contralateral side of the lesion, while preserving them on the ipsilateral side. Upon touching this side, the patient will not be able to localize where they were touched, only that they were touched. This is because fine touch fibers are carried in the dorsal column-medial lemniscus pathway. The fibers in this pathway decussate at the level of the medulla. Therefore, a hemi-section lesion of the spinal cord will demonstrate loss of both fine touch (preserved on the contralateral side) and crude touch (destruction of the decussated spinothalamic fibers from the contralateral side) on the ipsilateral side.

Pure Brown-Séquard syndrome is associated with the following:

– Interruption of the lateral corticospinal tracts:

• Ipsilateral spastic paralysis below the level of the lesion
• Babinski sign ipsilateral to lesion
• Abnormal reflexes and Babinski sign may not be present in acute injury.

– Interruption of posterior white column:

• Ipsilateral loss of tactile discrimination, vibratory, and position sensation below the level of the lesion.

– Interruption of lateral spinothalamic tracts:

• Contralateral loss of pain and temperature sensation. This usually occurs 2-3 segments below the level of the lesion.

Reference 1, Reference 2