Axons from the posterior hypothalamus descend through the mesencephalic and pontine reticular formations. The central processes of mesencephalic V neurons synapse in the motor nucleus V. The pseudounipolar neurons in the mesencephalic nucleus are embryologically derived from the neural crest. This circuit becomes overstimulated during a mesencephalic "fit". Primary cell bodies are in the mesencephalic nucleus of the trigeminal nerve. The pseudounipolar neurons in the mesencephalic nucleus carry proprioceptive information from the muscle of mastication. However, akinetic mutism most often appears in two different forms&colon; frontal and mesencephalic. This nucleus tapers into the lower mesencephalic reticular formation and contains sporadic giant cells. These descending pathways originate in the Mesencephalic Locomotor Region (MLR) and the lateral hypothalamus. Mesencephalic akinetic mutism is clinically categorized as somnolent or apathetic akinetic mutism. The mesencephalic nucleus is one of four trigeminal nerve nuclei, three sensory and one motor.