Page 17 - CASA Bulletin of Anesthesiology Vol 9 (4) 2022 (3)

Vol. 9, No 4, 2022

Keywords: plexiform neurofibroma; NF1; pediatric; Obstructive Sleep Apnea; laryngeal
lesion; airway management; anesthetic implication

Introduction

Neurofibromatosis Type1 (NF1), also known as von Recklinghausen disease, is the most
common form of Neurofibromatosis. It is a genetic disorder of the NF1 gene that regulates the
production of neurofibromin, a tumor suppressor and inherited in autosomal dominant fashion
with a high incidence of new mutations and significant clinical variability. While the estimated
incidence of NF1 is between 1 in 2500 and 1 in 3300 live births, its prevalence in the population
is approximately 1 in 4000 . NF-1 is characterized by cutaneous café au lait spots, peripheral
1
and central nervous system neurofibromas, and a spectrum of other tumors, particularly of the
central nervous system with highly variable expression that significantly impacts anesthetic care
2 . NF1 concerns include plexiform neurofibromas along with common clinical findings such as
cognitive and bony manifestations, macrocephaly, and optic gliomas. There are also very rare
findings that impact airway management, such as pharyngeal and laryngeal neurofibromas, that
may arise in the aryepiglottic folds and cause airway obstruction .
3
Mask ventilation or tracheal intubation can be further complicated by a multitude of issues
encountered including neck stiffness, facial bone deformities, macroglossia, or tumors of the
tongue or larynx. Atlanto-axial dislocation has been reported in patients with NF-1 and because
of the high incidence of spinal cord involvement, the anesthesiologist must exhibit extreme
caution manipulating the head for proper visualization of the vocal cords . Although benign
4
tumors occurring in the peripheral nerves are seen throughout the body, neurogenic tumors
arising primarily from the larynx are rare and include neurofibroma, schwannoma, and malignant
peripheral nerve sheath tumor. Owing to its slow growth and variability of location and size,
laryngeal neurofibromas can sometimes remain asymptomatic for years. Presenting symptoms of
these lesions include stridor, hoarseness, dysphagia, dysphonia, and globus sensation and are
usually progressive in nature .
5
The NIH “Natural History Study and Longitudinal Assessment of Children Adolescents, and
Adults with Neurofibromatosis Type 1” protocol has recruited a population of NF1 patients that
are followed for interval clinical evaluation of their disease manifestations. As part of their
evaluation, the pediatric study patients undergo a series of MRIs under anesthesia after a
thorough pre-anesthesia evaluation.

Case presentation

A 3 year old African American male with NF1 was enrolled in our NIH NF1 Natural History
Study and returned to the NIH for his annual MRI of brain/orbits and whole body. When queried
on new medical concerns, his mother reported the child was recently diagnosed with mild sleep
apnea based on a sleep study revealing an obstructive apnea/hypopnea index of 2.2 events per
hour with a low oxygen saturation of 86%. The symptoms were attributed to enlarged adenoids
and he was scheduled for an otolaryngology evaluation. His pre-operative NIH physical
examination was normal with the exception of an 8 mm mobile, non-tender subcutaneous nodule
of the right posterior neck suspicious for a subcutaneous neurofibroma.

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