Which cranial nerve exits the skull base at the pars nervosa of the jugular foramen?
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2 comments:
The glossopharyngeal (IX) passes thru there; the vagus and the accessory pass thru the pars venosa
You are correct.
The glossopharyngeal (ie, CN IX), vagus (ie, CN X), and accessory (ie, CN XI) nerves emerge cranial to caudal, in that order, from the ventral medulla, lateral to the medullary olive. From there, they course toward the jugular foramen and exit the skull base at the jugular foramen.
The glossopharyngeal nerve is located in the pars nervosa of the jugular foramen, and the vagus and accessory nerves are located within the more posterior pars vascularis. The hypoglossal nerve (CN XII) is formed by the fusion of multiple rootlets that emerge from the ventrolateral sulcus between the medullary olive and pyramid. The nerve exits the cranial vault via the hypoglossal canal, then lies medial to CN IX, CN X, and CN XI.
Schwannomas in the jugular foramen that arise from the glossopharyngeal, vagus, or accessory nerves, can present with variable cerebellar and acoustic symptoms, depending on the extent of the intracranial growth of the mass. They also can cause glossopharyngeal dysfunction (eg, hoarseness, difficulty swallowing) and/or spinal accessory symptoms (eg, trapezius atrophy).
Schwannomas of the jugular foramen are rare. Patients often present with symptoms consistent with eighth cranial nerve injury or cerebellar or brain stem compression. Symptoms relating to injury of the ninth or 10th to 12th cranial nerves are less common. Although the clinical presentation of a schwannoma of the jugular foramen may suggest the presence of a vestibular schwannoma, appropriate imaging techniques and interpretation should permit correct differentiation of tumor origin and type and suggest the appropriate surgical approach.
Schwannoma of the jugular foramen appears as a sharply demarcated, contrast-enhancing tumor, which is typically centered or based in an enlarged jugular foramen with sharply rounded bone borders having a sclerotic rim.
The clinical presentation of schwannomas of the jugular foramen varies significantly according to the tumor's growth pattern. Deafness, vertigo, and ataxia were present if the mass is intracranial. Most patients present with symptoms of decreased hearing; Hoarseness and weakness of the trapezius and sternocleidomastoid muscles occur in some patients in whom the tumor is within the bone or extracranial.
In patients with a large proportion of the tumor below the skull base, the symptoms tend to reflect glossopharyngeal injury.
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