Anesthetic Considerations for Chiari I Malformation in a BMI 62 Patient

ABSTRACT

Patients with Chiari I malformations present with tonsillar herniation below the foramen magnum causing abnormal spinal anatomy. Anesthesia challenges in this population include difficult airway management, monitoring intraoperative autonomic dysfunction, avoiding increased intracranial pressure, and accommodating sensitivity to neuromuscular blockade. We present a case with an additional airway management challenge due to morbid obesity with a BMI of 62. A 23 year old female with a history of Covid pneumonia and morbid obesity who presented with syringomyelia and Chiari I malformation. She initially presented with bilateral numbness, tingling, weakness, and pain in her hands. Imaging with MRI at the time showed downward displacement of the cerebellar tonsils with the tips reaching the lower portion of C1 and overall 10-12 mm displacement below the level of the foramen magnum. Syrinx was also visualized from the level of C1-C2 extending down to the level of T5-T6. Repeat MRI a year later showed no significant changes. However, she has worsening symptoms of pain in her right arm preventing her from working. She is agreeable to surgical decompression of the posterior fossa through a suboccipital craniotomy with resection of the posterior arch of C1 with duraplasty. Significant findings on the physical exam include Mallampati III, shorter thyromental distance, and limited range of motion of her cervical spine due to pain in her arms. We chose awake fiberoptic intubation due to difficult airway from morbid obesity and limited cervical spine range of motion and the consideration of hypercapnia induced from brief apnea the patient may not tolerate. She was premedicated with versed, glycopyrrolate, and dexmedetomidine, and given a 5% lidocaine paste lollipop to topicalize oropharynx. She was also started on a low dose remifentanil infusion for sedation during the awake fiberoptic approach. Blood pressure, heart rate, respiratory rate with continuous end-tidal capnography, and pulse oximetry were monitored during the awake fiberoptic intubation. A 7.0 endotracheal tube was lubricated with viscous lidocaine and placed over a fiberoptic scope. Once there was visualization of the vocal cords, additional 2% lidocaine was administered directly at the vocal cords. She was intubated smoothly on the first attempt. She was then immediately induced to general anesthesia with propofol and non-depolarizing muscle relaxant to avoid using succinylcholine due to the possible hypersensitivity caused by denervation. Intraoperatively, a conventional air warmer was used to prevent hypothermia. Invasive arterial blood pressure monitoring was applied. Normotensive blood pressure and normocapnia were maintained throughout the surgery. Muscular blockade was reversed with sugammadex at the end of surgery to ensure adequate ventilation especially with the patient's body habitus. Upon extubation, the patient had acute hypertension which was managed by nicardipine infusion and hydralazine boluses. Patient was taken to a neurosurgical intensive unit and monitored for two days. She was discharged home without any complication. In conclusion, anesthetic considerations for patients with Chiari I malformation include airway management, monitoring for autonomic dysfunction, avoiding increase in ICP, and optimizing postoperative neurological status with balanced anesthetic management.