Fasciculus Gracilis

fasciculus gracilis

The fasciculus gracilis is the medial part of the dorsal columns. It carries fine touch, vibration and position sense from the legs and lower trunk (below about T6). It is present at all levels of the cord and ends in the nucleus gracilis of the medulla.

Anatomical Data

Structure & Connections

Location	Medial part of the posterior funiculus, next to the posterior median septum, from the sacral cord to the medulla
Parts	Sacral, lumbar and lower thoracic fibres (layered from medial to lateral)
Connections	Dorsal root ganglia from T7 downward Nucleus gracilis Medial lemniscus (onward)
Blood Supply	Posterior spinal arteries

Biomechanics

Function & Actions

Conveys fine touch, vibration and conscious proprioception from the lower limbs and lower body on the same side.

Clinical Relevance

Clinical Notes

Because its fibres are the longest in the body, the fasciculus gracilis is often affected first in length-dependent disorders, so vibration loss at the toes and ankles is an early sign. In vitamin B12 deficiency and in hereditary spastic paraplegia, gracile fibres degenerate.

Pathology

Common Injuries & Conditions

Loss of Vibration Sense in the Feet

An early sign of dorsal column or large fibre nerve damage, as in B12 deficiency or diabetes.

Sensory Ataxia of the Legs

Unsteady gait with a positive Romberg sign from damage to the fasciculus gracilis.

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