Cuneate fasciculus

At a glance

English

Cuneate fasciculus

Latin (TA2)

Fasciculus cuneatus

System

Nerve

Region

Whole body

Side

Single, on the midline

About the cuneate fasciculus

The cuneate fasciculus, or tract of Burdach, is the outer of the two bundles that make up the posterior (dorsal) column of the spinal cord. It appears from about the sixth thoracic segment upwards and is therefore found only in the upper thoracic and cervical cord. On cross-section it is wedge-shaped, its broad base lying on the surface of the cord and its narrow edge pointing inwards. Medially it is separated from the gracile fasciculus by the posterior intermediate septum, and laterally it borders the posterior horn and the entering posterior roots.

Its fibres are the central processes of sensory cells in the spinal ganglia of the upper body. They arrive through the posterior roots and are, on average, thicker than those of the gracile bundle. Fibres entering at each new segment take up a position lateral to those already present, so the column is laid out in body order. Some fibres climb only a few segments and then enter the grey matter, where many end close to the cells of the posterior thoracic nucleus or form reflex links. Most, however, ascend all the way to the lower medulla without crossing.

In the medulla the fibres end in the cuneate nucleus, beneath the cuneate tubercle. Second-order fibres from that nucleus sweep forward as internal arcuate fibres, cross the midline and ascend as the medial lemniscus to the ventral posterolateral nucleus of the thalamus, which relays to the postcentral gyrus. This pathway carries discriminative touch, vibration and the sense of limb position for the arm, hand, neck and upper trunk.

Damage to the posterior columns causes loss of position sense, vibration sense and two-point discrimination on the same side below the lesion. Patients may be unsteady with eyes closed and clumsy at fine tasks such as identifying objects by touch, even when strength is normal.

Course and supply

Supplies

Carries fine touch, vibration and joint position sense from the upper limb, neck and upper trunk to the cuneate nucleus of the medulla, on the same side.

Blood supply

Supplied by the paired posterior spinal arteries.