Nerve
Corticobulbar tract
Descending commands for head and neck movement
High-yield
A unilateral supranuclear lesion commonly weakens the opposite lower face more than the forehead. If tongue weakness is evident, protrusion can deviate toward the weak side, away from the cerebral lesion. These patterns are clues, not absolute rules.
Overview
Corticobulbar fibers connect motor areas of the cerebral cortex with brainstem circuits controlling the face, jaw, tongue and throat. They descend through the corona radiata and internal capsule before reaching their targets at different brainstem levels. Many muscles receive cortical influence from both sides. Lower facial movement and tongue protrusion have a strong contralateral influence, rather than the entire hypoglossal nucleus receiving input from only one hemisphere.
Reference facts
- Origin
- Principally the face and head representation of the motor cortex, with contributions from other cortical motor areas
- Course
- Cortex → corona radiata → internal capsule, classically its genu → cerebral peduncle and brainstem motor circuits
- Motor
- Helps control voluntary movement of the face, jaw, palate, pharynx, larynx and tongue
- Sensory
- A descending motor pathway; it does not carry primary sensory information toward the cortex
Clinical correlation
Bilateral damage can produce pseudobulbar palsy: impaired speech and swallowing with slow, stiff tongue movements and an exaggerated jaw reflex. Involuntary laughing or crying may accompany it. Lower motor neuron disease instead can cause tongue wasting and fasciculations; some disorders produce both patterns.
Frequently asked questions
Where does the corticobulbar tract arise?
Principally the face and head representation of the motor cortex, with contributions from other cortical motor areas.
What muscles does the corticobulbar tract supply?
The corticobulbar tract supplies the helps control voluntary movement of the face, jaw, palate, pharynx, larynx and tongue.
What is the sensory distribution of the corticobulbar tract?
A descending motor pathway; it does not carry primary sensory information toward the cortex.
What is the course of the corticobulbar tract?
Cortex → corona radiata → internal capsule, classically its genu → cerebral peduncle and brainstem motor circuits.