Do intracranial and extracranial trigeminal afferents represent divergent axon collaterals?

Trigeminal nerves provide the principal afferent pathways for the transmission of intracranial and extracranial head pain. This study, using two retrograde axonal tracers, demonstrated that first division afferents projecting to intracranial and extracranial targets are not commonly axon collaterals of the same neuron. Therefore, divergent axon collaterals probably are not responsible for the phenomenon of referred pain within the first trigeminal division.