Lemniscus

Lemniscus is a term used in neuroanatomy to describe a bundle of secondary sensory fibers in the brainstem. The term is derived from the Latin word for "ribbon," reflecting the ribbon-like shape of these structures. There are three main types of lemnisci: the medial lemniscus, the lateral lemniscus, and the trigeminal lemniscus. Each of these structures carries specific types of sensory information from the body to the brain.

Medial Lemniscus

The medial lemniscus is a large ascending bundle of heavily myelinated axons that decussate, or cross over, in the brainstem. These axons carry information about touch, vibration sense, and proprioception (the sense of the relative position of one's own parts of the body) from the body to the thalamus.

Lateral Lemniscus

The lateral lemniscus is an ascending pathway in the brainstem that carries information about sound from the cochlear nuclei to the inferior colliculus. It is a major component of the auditory pathway and plays a key role in the processing of auditory information.

Trigeminal Lemniscus

The trigeminal lemniscus is an ascending pathway in the brainstem that carries sensory information from the face and head. This pathway is named after the trigeminal nerve, which provides the primary input to it.

Clinical Significance

Damage to the lemnisci can result in a variety of sensory deficits, depending on the specific lemniscus that is affected. For example, damage to the medial lemniscus can result in loss of fine touch and vibration sense, while damage to the lateral lemniscus can result in hearing loss.

See Also

• Neuroanatomy
• Brainstem
• Thalamus
• Trigeminal nerve