Outcome of Posterior Fossa Decompression with Duraplasty by Different Types of Graft in Patients with Chiari Malformation Type I

INTRODUCTION

Chiari malformation type I (CM-I) defined by descend of caudal end of the cerebellar tonsil and crowding of craniocervical junction ¹. About half to seventy percent of CM-I cases are accompanied by syringomyelia (SM), which may progressively develop to chronic and often irreversible myelopathy ^2,3. Although many people with CM-I are asymptomatic, some symptomes may be present as headache, cerebellar ataxia, ocular abnormalities, spasticity or lower cranial nerve involvement ⁴.

Suboccipital craniectomy with or without expansile duraplasty, arachnoid dissection, and tonsillar reduction are among the surgical options. Leakage of cerebrospinal fluid (CSF) is a frequent side effect of duraplasty. Incidence of CSF leak following durapasty varies between 2% and 11.7% ⁵.

Duraplasty may be performed using a variety of dural grafts, including autologous pericranium, allografts, xenografts, and synthetic substitutes. It is yet unknown if any of these materials are related with greater rates of CSF leakage or other adverse effects ⁶. Our rational was assess outcome and CSF leakage incidence according to type of dural graft in CM-I patients who managed by posterior fossa decompression and duraplasty.

PATIENTS AND METHODS

An interventional randomized study conducted at Department of Neurosurgery Surgery, Faculty of Medicine, Al-Azhar University during the period from 1 January 2020 to 1 December 2021. The study was accepted by Al-Azhar University's Ethics Board, and each subject signed an informed written permission form.

This study included twenty-eight patients with CM-I who underwent posterior fossa decompression with duroplasty were allocated in a simple randomised method without stratification in a 1:1 ratio to two equal groups: Group A “collagen matrix graft group”: (N=14): patients were treated with a dural substitute Engineered collagen matrix grafts (DuraGen; Integra Neurosciences, Plainsboro, NJ, USA). Group-B “fascia lata graft group”: (N=14): patients were treated with free tissue fascia lata graft. Asymptomatic patients and prior operation on the posterior cranial fossa were excluded.

All patients had complete history, neurological assessment and basal laboratory investigations. Magnetic resonance imaging (MRI) of the brain and craniocervical junction as well as computed tomography (CT) of the brain were done preoperatively.

We performed a midline suboccipital craniectomy, a y-shaped durotomy, a bipolar electrocautery method to shrink the cerebellar tonsils, and duroplasty either by DuraGen or fascia lata graft, watertight closure.

Clinical outcomes after surgery are classified as excellent, good, and poor ⁷. If all of the patient's preoperative neurological problems have been alleviated and he is able to resume his usual daily activities, the results were rated excellent. Partial enhancement in preoperative symptoms is good, as long as the patient can resume to his regular routine while poor outcomes are characterised as deterioration of the patient's neurological state and consciousness, or even death. We continue follow-up till 12 months.

Statistical analysis:

All data analyzed using statistical package for social sciences (SPSS) version 22 (SPSS Inc, Chicago, USA). For qualitative data, frequency and percent distributions was calculated. For quantitative data, mean, standard deviation (Sd) was calculated. significance was defined as P value < 0.05. The following tests were used; Mann-Whitney U test and Chi- Square test.

RESULTS

A total of twenty-eight patients with CM-I underwent posterior fossa decompression with duroplasty either by DuraGen graft or Facia lata graft, their mean of age was 30.71 +7.96 and 33.64 +11.27 years, respectively. The majority in both groups were females 64.3% and 57.1%, respectively. There was no significance between both groups regarding age and sex (Table 1).

Regarding symptoms in DuraGen and Facia lata group, the most prominent symptoms in both groups was occipital pain which presented in all patients followed by neck pain which presented in 78.6% and 71.4%, respectively without significance among both groups (Table 2).

Regarding clinical outcome, fascia lata group showed higher significant excellent rate (92.9%) than DuraGen group (57.1%)  (p=0.032) Figure 1. Also, one patient showed good outcome and none showed poor outcome in patients with fascia lata graft while there were four patients with good outcome, two with poor outcome in DuraGen graft patients without significance (Table 3) Figure 2.

Considering postoperative complications, only one patient (7.1%) in fascia lata group showed tight bandage while DuraGen group showed eight patients (57.1%) with CSF leakage (p=0.001), four patients (28.6%) needed reoperations (p=0.033), Figure 3  two cases (14.3%) with Aseptic meningitis and ten cases (71.4%) with tight bandage (p < 0.001) (Table 4).

The majority of both groups showed marked reduction in size of syrinx (64.3% and 78.6%) without significance (Table 5).

a  b

Fig. 1: a) MRI preoperative chiari type I b) postoperative using fascia lata

Fig. 2 : a) MRI preoperative chiari type I b) postoperative using dura Gen

a b c

Fig. 3: a) MRI preoperative chiari type I b) postoperative using duragen c) after repair using fascia lata 

Table 1: Demographic data of studied patients

Table 2: Distribution of symptoms in studied patients

*p value was significant

Table 3: Clinical outcome after surgery

*p value was significant

Table 4: Postoperative complications in studied patients

Table 5: Size of syrinx after surgery