Acute Respiratory Arrest Following Partial Suboccipital Cranio- Plasty for Cerebellar Ptosis from Chiari Malformation Decom- Pression

Neurosurg Focus 25 (6):E12, 2008

Acute respiratory arrest following partial suboccipital cranioplasty for cerebellar ptosis from Chiari malformation decompression

Report of 2 cases

Xi a o Di, M.D., Ph.D.,1 Ma r k G. Lu c i a n o , M.D., Ph.D.,1 a n d Ed w a r d C. Be n z el , M.D.2 1Section of Pediatric and Congenital Neurosurgery, and 2Center for Spine Health, Neurological Institute, Cleveland Clinic, Cleveland, Ohio

Cerebellar ptosis is a rare complication following Chiari malformation decompression, and generally is the result of a very large suboccipital craniectomy. This can lead to the descent of the cerebellum through the craniectomy defect, which in turn may result in cerebellar herniation through the surgical defect as well as the reestablishment of contact between the cerebellar tonsils and the brainstem. In addition, dorsal adherence of the herniated cerebellum to the dura mater or dural patch and an associated obstruction of cerebrospinal fluid flow at the cervicomedullary junction may ensue. Such a result is not desirable, in that it reproduces or mimics the pathoanatomical relationships that existed prior to the surgical decompression. (DOI: 10.3171/FOC.2008.25.12.E12)

Ke y Wo r d s • cerebellar ptosis • Chiari malformation • respiratory arrest

a r t i a l suboccipital cranioplasty is effective in Both were reintubated and monitored in an intensive care treating cerebellar ptosis. We report respiratory ar- unit. One was extubated within 24 hours and discharged rest following partial suboccipital cranioplasty for home 1 week postoperatively. Extubation failed twice in Pcerebellar ptosis secondary to CM decompression in 2 the other, and a prolonged mechanical ventilation, with patients. The first patient was a 50-year-old woman with the performance of a tracheostomy, ensued. Recovery to a 1-year history of recurrent symptoms following de- a near independent state was achieved. compression of CM performed 2 years previously. The Cerebellar ptosis is a condition that is potentially second patient was a 66-year-old woman with a 4-year remediable via partial suboccipital cranioplasty. These history of progressively worsening symptoms that were patients may be at a relatively high risk for respiratory characteristic of her CM symptoms experienced 7 years arrest. prior (Table 1). Admission MR imaging revealed the presence of severe cerebellar ptosis with excessive cerebellar tonsil descent (Fig. 1 left) in both patients. These Case Reports patients both underwent a standard partial suboccipital Case 1 cranioplasty performed by different senior surgeons at our institution (Fig. 1 right). A large suboccipital craniec- History. This 50-year-old right-handed woman pre- tomy was identified in both intraoperatively, with the cer- sented with a recurrent and intractable headache, and ebellar hemisphere protruding out of the decompression with a gait problem that had continued for 6 months. She window (Fig. 2). Fifteen and 72 hours postoperatively had undergone CM decompression in another hospital ~ (in Cases 2 and 1, respectively), the patients experienced 2 years before. similar episodes of apnea and subsequent respiratory arrest. Postoperative MR images and emergency CT scans Examination. On examination, the patient was alert were negative for bleeding, infarct, and blockage of the and oriented but dehydrated, and she was in a wheelchair CSF pathway (Fig. 3). Chest radiographs revealed no ev- due to headache with nausea and vomiting, imbalance, idence of pulmonary aspiration in either patient (Fig. 4). and dizziness. The MR imaging showed no evidence of ventriculomegaly and syrinx, but it did show cerebellar hemispheres with tonsils descending down through the marked occipital craniotomy (Fig. 1 left). Abbreviations used in this paper: CM = Chiari malformation; CM-I = CM Type I; MMA = methyl methacrylate. Operation. Intraoperatively, a large (5 × 4–cm)

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Fig. 1. Case 1. Admission MR imaging (left) revealing ptosis of cerebellar hemispheres through the marked occipital craniotomy, and postoperative MR imaging (right) showing the cranioplasty placed and no acute hydrocephalus, infarct, or hematoma. boundary of the former suboccipital craniectomy was Postoperative Course. Postoperatively, the patient found, and the descended cerebellar tonsils and the cervi- was able to be out of bed and walking without assistance cal spinal cord were clearly seen intact (Fig. 2). A good on postoperative Day 1 and ambulated on Day 2. On Day CSF flow from the foramen of Magendie was noticed af- 3, the patient suddenly suffered respiratory distress and ter the dura mater was opened at the cervicomedullary was intubated immediately. Chest radiographs confirmed junction in the midline. Alloderm duraplasty was used to there was no infiltrate, and a head CT scan was negative close the dura with a 4–0 suture in a watertight fashion. in the posterior fossa, with no evidence of acute hydro- Attention was then turned toward the creation of the new cephalus or infarct. The patient recovered, was extubat- posterior fossa floor for treatment of ptosis and cerebel- ed within 24 hours, and was discharged on Day 7. Two lar support. This was fashioned from titanium mesh and weeks after being discharged the patient walked into the MMA, and secured with 4 screws around the perimeter clinic, with preoperative headache and imbalance having of the cranioplasty. The cranioplasty was formed in such completely resolved. The patient remains well on annual a way as to reduce the large craniectomy, from ~ 4–5 cm follow-up examinations. down to a 2 × 2–cm craniectomy. Care was taken not to allow any sharp edges and or any compression of the Case 2 cerebellum or cervicomedullary junction by the cranioplasty. The cranioplasty was seated well and secured over History. This 66-year-old right-handed woman pre- the duraplasty. The incision was then irrigated and closed sented with a 4-year history of mild headache, dizziness, in layered fashion with a running absorbable suture for difficulty in swallowing, 2 years of gait imbalance, and 1 skin closure. year of progressive numbness in the face and upper ex- tremities. The patient reported that she had recently experienced occasional urinary incontinence. She had re- ceived a diagnosis of CM-I and had undergone her CM decompression 7 years earlier at a different institution. Examination. The patient was alert and oriented, with stumble gait. She showed absent gag reflex on the right side. Admission MR imaging showed tonsil herniation without syrinx. Operation. During the operation, the cerebellar tonsils were indeed found protruding in a conical fashion through the foramen magnum and pushing on the medulla at the level of the obex. There was no CSF seen initially emitting from the obex. With the aid of bipolar cautery, cerebellar tonsils were coagulated in both a caudal and a cephalad direction. Once the tonsils were cauterized, CSF began emitting from the obex of the fourth ventricle. Fig. 2. Case 1. Intraoperative photograph showing the large (5 × 4 Some subarachnoid adhesions were loosened using the cm) former suboccipital craniectomy that was found and the descended microscissors. A small piece of ligamentum nuchae was cerebellar hemispheres (arrows) that were seen through the bone win- removed, and this was used as a pericranial graft. The dow. graft was sutured in place with 4–0 Nurolon sutures in a

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Fig. 3. Case 2. Admission head CT scan, which was negative for acute hydrocephalus, infarct, or postoperative hematoma in the pos- Fig. 4. Case 2. Chest radiograph revealing no evidence of pulmo- terior fossa. nary aspiration after emergency intubation. continuous running fashion. Then, using the drill with the cele,16,25 meningitis,4 CSF leakage,25 and cerebellar pto- M8 bit, we made circumferential divots in the preexist- sis.8 The latter is a complication with potentially severe ing shelf of bone to accept the MMA and create a mortis consequences, and its incidence has probably been un- and wedge type of interface to hold the glue. Once mixed derestimated. Cerebellar ptosis is generally the result of and in the hardening stages, we conformed the MMA to a prior suboccipital craniectomy that is > 4 × 4 cm from create a shelf that contained the contents of not only the the estimated edge and center of the foramen magnum. duraplasty but also the posterior fossa, and allowed a gen- Patients with cerebellar ptosis characteristically present erous ring of foramen magnum (~ 2 × 2 cm). The MMA with intractable headaches, neck pain, suboccipital burn- was undermined under the divots, thus conforming to the ing sensation, dizziness, nausea, swallowing problems, valleys of the divots. and imbalanced gait. Partial suboccipital cranioplasty has been used to treat the cerebellar ptosis because symp- Postoperative Course. The patient did well through- tomatic cerebellar ptosis almost always follows excessive out the postanesthesia care, and was transferred to the decompression of CM.8 regular neurosurgery nursing unit. Approximately 15 We attribute the symptoms of cerebellar ptosis in part hours postoperatively, the patient experienced acute re- to a damaged brainstem resulting from chronic compres- spiratory failure. Results of the emergency CT scan were sion. This results in a further worsening of the ptosis and negative (Fig. 3), and the chest radiograph revealed no associated symptoms; the latter include respiratory arrest. evidence of pulmonary aspiration (Fig. 4). The patient An awareness of the increased potential for such a com- was then reintubated and placed on ventilation in the in- plication should minimize the incidence of catastrophic tensive care unit. Extubation failed twice in this patient, sequelae. and a prolonged ventilation weaning period was antici- The goal of surgery for CM-I is to decompress the pated. Subsequently, on postoperative Day 8, the patient cerebellar tonsils and the upper cervical spinal cord and underwent a tracheostomy and percutaneous endoscopic to restore the flow of CSF in the subarachnoid space in gastrostomy. Since then, she has been fed by tube via the region of the cervicomedullary junction. Treatment of percutaneous endoscopic gastrostomy. The patient was the adult form of this condition presents a much greater admitted to the subacute care facility for rehabilitation, challenge to the neurosurgeon. Most authors agree that and then was transferred to a nursing home, where she is treatment should consist of a suboccipital craniectomy living dependently. and upper cervical laminectomy to decompress the malformation at the foramen magnum.6,7,18,24 However, CM Discussion decompression may lead to cerebellar ptosis if the suboccipital craniectomy is excessive.3,8,26 In some patients The treatment of CM-I remains challenging and the material used for dural grafting may also play a role, controversial. This is especially so regarding surgical op- often due to dural tension related to scarring. Although it tions. These include the size of the suboccipital craniec- is recognized that some surgeons favor a wide posterior tomy, a decompression with or without an opening of fossa craniectomy, others have opted for a small craniec- the dura mater, an opening of the dura with or without tomy in the treatment of CM-I.10 The most common man- closing or patching with dural graft, tonsillectomy, and agement strategy selected for this complication is partial so on.1,2,12,19,21,22,24 Overall, surgery has proven to be quite cranioplasty, with or without intradural exploration. Du- effective.6,18,24 The most frequently reported complica- raplasty was performed in both of our cases to attain ad- tions following CM surgery include pseudomeningo- equate restoration of CSF flow from the fourth ventricle.

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TABLE 1: Characteristics in 2 patients with respiratory arrest following suboccipital cranioplasty for cerebellar ptosis*

Age Previous Change Postop (yrs), CM Op Onset of Preop Hy- in Ventricle Compli- Aspiration/ Sex (yrs) Preop Symptoms RA (hrs) drocephalus Size cations Infection 50, F 2 intractable HA, neck pain, extrem- 72 shunt no no no ity weakness placed 66, F 4 constant HA, neck pain, vertigo, 15 no no no no swallowing difficulty, incontinence, spastic gait, absent gag reflex

* HA = headache; RA = respiratory arrest

Alloderm was sutured as dural graft in one case, and a have been unable to find any report of sudden, unpro- piece of ligamentum nuchae was used in the other. The voked respiratory arrest following suboccipital cranio- previous craniectomy sizes were found > 4 × 4 cm from plasty in adults with cerebellar ptosis. In both of our pa- the edge of the foramen magnum in both cases. The cres- tients, the radiological and operative findings suggested cent-shaped cranioplasty reduced the craniectomy to ~ 2 compression of the brainstem and spinal cord due to the × 2 cm in both cases. The patients partially recovered and cerebellar ptosis. The patient in Case 1 has a shorter his- were transferred from the intensive care unit to a ward. A tory regarding both the initial diagnosis of CM and the respiratory arrest occurred at 15 and 72 hours following recurrent symptoms from cerebellar ptosis, whereas the the surgeries in Cases 2 and 1, respectively. one in Case 2 was observed to have a greater disturbance Respiratory failure following suboccipital craniec- of lower cranial nerves. The latter may indicate that the tomy frequently involves an intraoperative injury to the secondary injury from the recurrent cerebellar ectopia brainstem, or secondary compression or herniation from might add to the neurological impairment, in turn making the postoperative hematoma and via acute obstructive hy- the involved brainstem more susceptible to further injury drocephalus. Postoperative imaging and emergency CT and subsequent respiratory arrest. scans after respiratory arrest in the 2 patients presented here demonstrated no evidence of intraoperative trauma, Conclusions postoperative bleeding, or hydrocephalus (Fig. 3). In 1983, Park et al.17 reported a series of 45 infants with myelom- The risk of sudden respiratory arrest as well as grad- eningocele and hydrocephalus, in which 28 (62%) of the ual respiratory deterioration must be considered in plan- patients were alive and 17 (38%) had died at the last fol- ning the management protocol in patients with cerebellar low-up assessment after decompression of CM. The ma- ptosis. Indeed, they may have a postoperative course and jority of deaths were attributed to respiratory failure. Paul ultimate outcome that is less successful than expected et al.18 reviewed 71 cases of CM-I. All patients underwent with a de novo CM decompression operation. suboccipital craniectomy and C1–3 laminectomy. Respi- ratory depression was the most frequent postoperative Disclaimer complication (14%). One patient died of sleep apnea 36 The authors report no conflict of interest concerning the mate- hours after the operation. Additionally, acute respiratory rials or methods used in this study or the findings specified in this arrest has been reported previously at 2, 3, and 42 hours, paper. and as late as 2 months after suboccipital craniectomy for 5,9,14,27 CM-I. Sudden respiratory deterioration due to the Acknowledgment initial procedure has been described, possibly as a result of the loss of respiratory center neurons in the morbid The authors thank Ms. Christine Moore for her kind assistance condition, with this loss possibly due to congenital de- with the preparation of this manuscript. formity or lengthy compression.15,23 Although there was no obvious tether identified intraoperatively on the spinal References cord or brainstem in either case, one wonders if stretch- 1. Asgari S, Engelhorn T, Bschor M, Sandalcioglu IE, Stolke D: ing on the vulnerable cervicomedullary junction from the Surgical prognosis in hindbrain related syringomyelia. Acta elevation of the cerebellum during the cerebellar shelving Neurol Scand 107:12–21, 2003 procedure is possibly responsible. Besides, it might be that 2. Bell WO, Charney EB, Bruce DA, Sutton LN, Schut L: Symp- some of the compromised vasculature (including arteries tomatic Arnold-Chiari malformation: review of experience and veins) played a certain role in the catastrophic com- with 22 cases. J Neurosurg 66:812–816, 1987 plication as well, which has been reported sporadically in 3. Cocolina J, Galvan M, Medrano P, Caceres A, Eiras J, Lopez- 11,13,20 Pison J: Episodes of unilateral sympathetic hyperfunction, patients with CM-I. changes in consciousness status and respiratory dysfunc- Both patients presented here, however, had neuro- tion in a girl with type II Chiari malformation. Rev Neurol logical abnormalities for years following suboccipital 31:745–748, 2000 craniectomy and C-1 laminectomy due to their CM. We 4. Fischer EG: Posterior fossa decompression for Chiari I de-

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