Airway Obstruction After Ventriculoperitoneal Shunt Insertion in a Patient with Neurofibromatosis

Abstract

We present a case of postoperative upper airway obstruction in a patient with neurofibromatosis (NF) type II after placement of a ventriculoperitoneal (VP) shunt, most likely related to upward transtentorial herniation of the brainstem or compression of the involved cranial nerves. Case Report A deaf, mentally retarded, 60-kg, 18-yr-old male with NF, hydrocephalus, and associated increased intracranial pressure (ICP) was scheduled for elective VP shunt placement. Past surgical history included a number of surgical procedures (craniotomy and gamma knife) to decrease intracranial tumor mass. The increased ICP was due to brainstem compression and secondary obstruction of cerebrospinal fluid flow by two large cerebellopontine angle tumors. Small nerve sheath tumors of the left cranial nerves IX and XII were present, as well as tumors arising from cranial nerves III, IV, and V. The patient suffered from symptoms of upper airway obstruction upon falling asleep for the last year, but the cause for this had not been fully elucidated. He aspirated occasionally when eating and drinking. Increased ICP was diagnosed by magnetic resonance imaging and by the presence of papilledema. Anesthesia was induced with thiopental 250 mg, fentanyl 100 micro g, and rocuronium 60 mg intravenously to facilitate rapid sequence endotracheal intubation. The trachea was easily intubated with an 8.0-mm endotracheal tube. No upper airway abnormality was noted during laryngoscopy. The case proceeded uneventfully, and at the end, neostig-mine 2.5 mg/kg and glycopyrrolate 0.6 mg/kg were administered intravenously to reverse residual neuromuscular blockade, as assessed clinically and with a nerve stimulator at the ulnar nerve. The patient was tracheally extubated while awake and breathing spontaneously, with adequate tidal volumes. Upon arrival in the postanesthesia care unit, the patient developed upper airway obstruction that was easily relieved by a jaw thrust. Although the patient was fully awake, he obstructed if jaw thrust was released. Nasopharyngeal airways were inserted bilaterally, but the patient remained unable to maintain his airway. He was anesthetized, and his trachea was easily reintubated with no airway pathology noted at direct laryngoscopy. He was transferred to the neurosurgical intensive care unit. A brain computerized tomography scan shortly after admission to the neurosurgical intensive care unit excluded bleeding and shunt malposition. In the successive 7 days, three separate extubation attempts failed. On each occasion, the patient immediately developed upper airway obstruction similar to that in the postanesthesia care unit. After a week, a tracheostomy was performed. Examination at that time revealed no masses, normal anatomy of the pharynx and larynx, and normal vocal cord function. The patient was discharged shortly thereafter, with no other sequelae. Discussion This is the first reported case of acute upper airway obstruction associated with decompression of increased ICP after VP shunt. Patients suffering from neurofibromatosis present a host of anesthetic considerations. Kyphoscoliosis may cause restrictive lung disease, compounded by fibrosing alveolitis in up to 20% of patients [1]. Up to 5% of NF patients have intraoral manifestations of the disease. Crozier [2] described a large neurofibroma at the base of the tongue causing acute upper airway obstruction after induction of anesthesia, requiring emergency tracheostomy. Sleep apnea syndrome has also been described in patients with NF, due to superior venacaval obstruction causing upper airway edema [3]. Our patient did not have any signs, symptoms, or radiographic correlates of superior venacaval obstruction. In our patient, the etiology for the upper airway obstruction was clearly not due to local anatomical variants or masses as revealed by repeated direct airway examination. Preoperatively, the patient was able to maintain a patent airway when awake; he suffered acute upper airway obstruction postoperatively. He developed no further neurological signs other than the inability to maintain a patent airway, despite returning to his preoperative level of consciousness. Magnetic resonance imaging studies performed shortly before surgery (Figure 1) revealed severe compression of the brainstem and lower cranial nerves. Motor innervation of the tongue, pharynx, and larynx is derived from cranial nerves XII, IX, and X, respectively. Two of these nerves had neurofibromas arising from their sheaths. Neuroconduction studies of the involved cranial nerves were not performed because preoperative tumor involvement of the nerve sheaths of cranial nerves IX and XII was present. A positive result would not have differentiated new from preexisting nerve damage.Figure 1: Magnetic resonance imaging scan showing compression of the brainstem by two large tumors in the cerebropontine angles.After decompression, the patient developed acute upper airway obstruction due to his inability to control his upper airway. Upward transtentorial herniation has been described after VP shunt insertion for increased ICP due to a posterior fossa tumor. We suggest that our patient suffered either a degree of upward transtentorial herniation due to the acute changes in the delicate balance of forces that existed prior to shunt insertion or compression of the involved cranial nerves. In patients developing acute postoperative upper airway obstruction, a broad differential diagnosis may be entertained. In this case, we demonstrated that ICP changes after VP shunt insertion resulted in neurological deficits causing upper airway obstruction. The authors thank Jacques Chelly, MD, PhD, for his continued support and advice.