Introduction: Chiari’s malformation refers to a group of disorders consisting of congenital displacement of the Hindbrain. Chiari I malformation (ACM-I) consists of downward displacement of the cerebellar tonsils into the spinal canal, leading to a cerebrospinal fluid (CSF) obstruction and idiopathic intracranial pressure (ICP). There is a paucity of cases on the anesthetic management in pregnant patients with ACM. We present a case of a patient with ACM-I and idiopathic intracranial hypertension, compounded by super morbid obesity for repeat cesarean section (CS).
Case description: A 31 y.o. G4P3003 at 39w2d scheduled for repeat CS. Her past medical history includes: (ACM-I) with an 11mm tonsillar herniation, pseudotumor cerebri, syrinx of cervical spinal cord, chronic migraines, vertigo, and gestational diabetes. Past surgical history includes cholecystectomy and three CS. Patient had been on acetazolamide for pseudotumor cerebri which was stopped at the onset of pregnancy. Other pertinent history and physical includes a BMI of 54.3 and absence of elevated ICP.
After informed consent was obtained, a combined spinal epidural (CSE) was performed under sterile fashion in the sitting position. Using a midline approach, a 18G 3.5 inch Tuohy needle was advanced with a loss of resistance technique with saline and the epidural space was identified at a depth of 7 cm. A 27 ga 4 11/16 inch Whitacre spinal needle was advanced through epidural needle and after clear CSF, bupivacaine 12 mg, fentanyl 20 mcg and PF morphine 150 mcg was administered. A 20 ga catheter was then threaded into the epidural space. She underwent an uncomplicated classical CS. Due to the length of the case, 3 ml of lidocaine 2% was administered via the epidural catheter towards the end of the case to extend anesthesia coverage. Patient had a satisfactory recovery and was discharged three days later without any anesthetic or neurologic complications.
Conclusion: ACM-I is a rare disorder and consists of the downward displacement of the cerebellar tonsils through the foramen magnum. This case was quite challenging due to her large BMI, three previous CS and pseudotumor cerebri. Although there is a paucity of cases of ACM and pregnancy, both general and neuraxial anesthesia have been used in these cases. General anesthesia carries the risk of hypoxia, and a hypertensive response with subsequent increased in ICP especially on induction and emergence. However, an elevated ICP would be a contraindication for neuraxial anesthesia, with the potential for herniation, especially with an accidental dural puncture with an epidural needle. However, in light of a normal ICP and the potential surgical technical difficulty with this case, we chose to perform a careful CSE and utilize a small spinal needle with good results.
Ultimately, each case should be individualized, evaluating risks and benefits along with the mode of delivery and utilizing a multidisciplinary approach.