Anatomy clinical correlates: Glossopharyngeal (CN IX), vagus (X), spinal accessory (CN XI) and hypoglossal (CN XII) nerves

The glossopharyngeal, vagus, spinal accessory, and hypoglossal nerves, also known as cranial nerves IX, X, XI, and XII, respectively, all combine to carry sensory, motor, and parasympathetic innervation to the pharynx, larynx, tongue, and many other regions. Injury of these nerves can affect important functions like swallowing, the gag reflex, breathing, and even cardiac output. Now, we know that cranial nerves can be a hard pill to swallow, but soon you’ll see that by knowing the anatomy and the important functions of these nerves, the clinical presentations and the management of these injuries isn’t so difficult to understand.

First, let’s discuss bulbar palsy, which refers to a unilateral lower motor neuron lesion of cranial nerves IX, X, XI and XII, and it’s caused by a lesion in the medulla that affects the nucleus ambiguus and the hypoglossal nucleus. Symptoms are associated with impaired function of the affected nerves. For example, if the glossopharyngeal nerve is damaged, this causes difficulty with swallowing. Other common symptoms include nasal regurgitation, slurred speech, and difficulty speaking. Also, reflexes like the gag reflex and jaw jerk are usually absent.

Pseudobulbar palsy, on the other hand, refers to a bilateral upper motor neuron lesion of cranial nerves XI, X, XI and XII, caused by more supra nuclear proximal damage to motor fibers somewhere between the cortex and the medulla leading to an upper motor neuron injury. The symptoms are similar to bulbar palsy, however, the gag reflex and jaw jerk are usually overactive, which if you remember, is indicative of an upper motor neuron lesion.