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Chromosome 13
14%
1/7
Chromosome 7
Chromosome 17
Chromosome 22
57%
4/7
The X chromosome
0%
0/7
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This patient's tinnitus, vertigo, and hearing loss comprise the classic signs and symptoms of bilateral schwanommas (aka acoustic neuromas), which occurs in neurofibromatosis type II (NFII), a neurocutaneous syndrome. This condition is associated with a mutation in the merlin gene, found on chromosome 22. Acoustic neuromas present with tinnitus, vertigo and hearing loss. It can also be visualized on MRI. An important diagnostic marker associated with acoustic neuromas is that they are S100+ (as are most neural crest cell derived tumors). The autosomal dominant mutation in NFII is in merlin on chromosome 22. This mutation leads to uncontrolled schwann cell proliferation via impairment in E-cadherin-mediated contact inhibition. Li et al. states that tumor size is a significant prognostic indicator for acoustic neuromas. Classically, measurement has focused on linear size rather than the volume of the acoustic neuroma. Li et al. concluded that volume is the best prognostic indicator and that standardization needs to be done when it comes to measuring acoustic neuromas in order to have a more reliable method of determining prognosis. Setty et al. states that management of acoustic neuromas can be done endoscopically. Setty claims that a purely endoscopic approach for surgical management of patients with acoustic neuromas is a safe option and can preserve hearing in an appropriate patient population. Figure A demonstrates an MRI of a patient with bilateral acoustic neuromas. In this image the lesions are quite prominent and appear as white (schwann cells) material surrounding CN VIII (Note CN VIII is not visible on MRI). Note that such prominent lesions would likely be associated with more symptoms and this figure was chosen to illustrate a clear example of bilateral acoustic neuromas. Incorrect answers: Answer 1: A trisomy of 13 is seen in Patau's syndrome. Answer 2: A mutation in chromosome 7 can be seen in osteogenesis imperfecta. Answer 3: A mutation on chromosome 17 is seen in neurofibromatosis type I. Answer 5: A mutation in the X chromosome can be seen in Fragile X syndrome, a CGG X-linked recessive trinucleotide repeat disorder.
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