DISORDERS OF THE HYPOGLOSSAL NUCLEUS AND NERVE Supranuclear lesions affecting the corticobulbar fibers above their decussation result in weakness of the contralateral half of the tongue. Bilateral upper motor neuron…

The cranial root is the smaller of the two portions of the accessory nerve. Although it is discussed in this section, it is often considered as a part of the…

Oculomotor Nuclei. The somatic and parasympathetic efferent fibers in the oculomotor nerve are the axons of cells located in the complex oculomotor nuclei situated anterolateral to the upper end of…

Motor Neurons. Except for muscles innervated by the cranial nerves, each somatic muscle receives its motor supply from a column of motor neurons arranged longitudinally in the anterior horn of…

The facial nerve can be damaged at any level along its course (Plate 1-27). Facial musculature paralysis is the hallmark of seventh cranial nerve lesions. The presence or absence of…

The cochlea receives dual innervation: afferent fibers, which originate from cell bodies in the adjacent spiral ganglion efferent fibers, which originate in the brainstem. Both types of fibers form synapses…

FACIAL NERVE DISORDERS Facial weakness is caused by both central and peripheral lesions, and differentiating between the two frequently requires close examination. Peripheral facial weakness involves both the upper and…

OTHER ETIOLOGIES OF FACIAL NEUROPATHY Lyme disease is a relatively common infectious cause of an acute unilateral or bilateral facial neuropathy. Symptoms typically include systemic symptoms (e.g., arthralgia, fever, rash),…

Posterior Horn. Many neurons in the six laminae of the posterior horn receive direct synaptic input from spinal afferent fibers that enter the spinal cord via the posterior roots and…

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