HSC Section 3 - Trauma, Critical Care and Sleep Medicine

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Pontine Vascular Malformations Vascular malformations, including arteriovenous malformations (AVMs) or venous malformations (VMs) may be located in the brainstem. These lesions expand over a patient’s lifetime and may cause compression or hemorrhage with resultant neurologic deficit or mortality (headache, seizure, focal deficit). Brainstem AVMs are high-flow lesions that may remain asymptomatic until an acute hemorrhagic event. In patients with syndromes associated with AVMs, such as hereditary hem- orrhagic telangiectasia, capillary malformation–AVM, or a PTEN mutation, MRI screening may lead to an earlier diagnosis. VMs, on the other hand, are low- flow vascular malformations. Expansion, especially in the cerebellopontine angle, can cause FP. Treatment for AVMs will depend on the size and extent of the lesion and includes observation, surgery, embolization, or a combined embolization and surgery, or radi- ation. 60,61 In general, the brainstem is very sensitive to radiation effects and therefore this is not a favored option. Treatment for VMs also includes observation, surgery, sclerotherapy, or a combined approach.

FAMILIAL

There is an association with paralysis of multiple facial nerve branches and specific alleles 3q21 to 22 with autosomal dominant transmission. However, no gene has yet been identified. 62 There are also known families with an history of BP and no iden- tified gene defect. This may be related to a structural narrowing of the intraosseous facial nerve canal that predisposes these individuals to BP.

PEDIATRIC CONSIDERATIONS

The most common cause of pediatric acute FP is also BP 63 followed by other infec- tious causes (zoster, otitis media), and trauma. In a study of 975 patients at a large Korean medical center, the most common causes in pediatric and adult cases were the same. However, children had a better prognosis than adults.

BILATERAL FACIAL PARALYSIS

BFP represents 0.2% to 3% of all cases of FP. 21,64 The paralysis may occur simulta- neously or in succession. The most common cause of BFP is BP followed by Lyme disease. Regarding timing of paralysis, the most common cause of simultaneous BFP is Lyme disease, followed by posterior fossa tumors, trauma, immune- mediated GBs, central nervous system lymphoma, and HIV infection. In asynchronous cases, BP was the most common, followed by NF-2–associated vestibular schwan- noma and MRS. 64–66

ACUTE RECURRENT FACIAL PARALYSIS

Recurrent FP warrants investigation into other diagnoses apart from BP. An MRI should be considered to rule out tumor as well as diagnostic laboratory studies for endocrine, metabolic, autoimmune, or other systemic causes.

DIAGNOSTIC TESTING Laboratory Testing

Laboratory testing should be tailored to the individual history and physical examination. Patients with a history and physical consistent with BP do not require diagnostic testing,

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