Major research findings

Chiari malformation is a condition where the cerebellar tonsils descend through the foramen magnum, potentially causing symptoms from compression or obstruction of the flow of cerebrospinal fluid. 13 , 14 Diagnosis and treatment of Chiari malformation can vary, and guidelines produced through systematic review may be helpful for clinicians. 13 , 14

Chiari malformation Type I (CM-I) is a common and often debilitating neurological disease. 3 Efforts to improve treatment of CM-I are impeded by inconsistent and limited methods of evaluating clinical outcomes. 3 To understand current approaches and lay a foundation for future research, the authors conducted a systematic review of the methods used in original published research articles to evaluate clinical outcomes in patients treated for CM-I. 3

The best surgical treatment for adult Chiari malformation type 1 remains widely debated. 10

Chiari malformation type 1 (CM-1) is a variation of hindbrain development that can sometimes occur in asymptomatic individuals. 5 Conventional treatment is surgical decompression, but little is known about the natural history of patients who do not undergo surgical management. 5 This information is critical to determine how these patients should be managed. 5 We conducted a systematic literature review to determine the natural history of CM-1, particularly in patients who did not undergo surgery and in asymptomatic individuals, to help patients and physicians determine when surgery is likely to be beneficial. 5

The current surgical management of adult Chiari malformation type I (CM-I) with associated syringomyelia remains controversial. 12 The objective of this study was to explore posterior fossa decompression and duraplasty (PFDD) with and without tonsillar resection in adult patients with CM-I and syringomyelia. 12

Surgery for Chiari malformation Type I (CM-I) is one of the most common neurosurgical procedures performed in children, although there is clearly no consensus among practitioners about which surgical method is preferred. 1 The objective of this meta-analysis was to compare the outcome of posterior fossa decompression with duraplasty (PFDD) and posterior fossa decompression without duraplasty (PFD) for the treatment of CM-I in children. 1

Hemifacial spasm (HFS) can be associated with Chiari malformation type I (CM1), but the treatment paradigm for these concurrent conditions has not been well-defined. 11 We sought demographical differences between patients with HFS with and without CM1 and explored optimal surgical treatments for these patients. 11 A systematic review of peer-reviewed literature identified 8 studies with 51 patients with CM1 and HFS. 11 A patient from the authors' institution is presented as a case illustration. 11 Of the 51 patients, the average age was 39.4 years, 63% (32/51) were female, 73% (37/51) underwent microvascular decompression (MVD) as a primary intervention, and 16% (8/51) underwent suboccipital decompression (SOD). 11 After primary MVD, 83.7% (31/37) had complete resolution of their symptoms and 10.8% (4/37) had either recurrent CM1 symptoms or new-onset CM1 symptoms. 11 Three (8.1%) required reoperation with suboccipital decompression to address new CM1-related symptoms. 11 All patients who underwent SOD first had complete or near-complete resolution of symptoms. 11 In 3 patients (37.5%) with near-complete resolution, the residual symptoms had insignificant impact on their quality of life. 11 These data suggest that concomitant CM1 should be among the differential diagnosis in younger patients who present with HFS, particularly those who are female or who present with history suggesting tussive headaches. 11 For patients who present with HFS and headache with CM1, SOD instead of MVD may be the preferred surgery to address concurrent symptoms. 11 In patients with HFS and CM1 without headache, optimal treatment is less clear, but SOD as initial surgery may obviate the need for future reoperation. 11

Posterior fossa decompression (PFD) is commonly applied as treatment for Chiari malformation type 1 (CM1), an entity which is associated with a variety of presenting symptoms but little data correlating symptoms to surgical outcome. 2 We applied the Chicago Chiari Outcome Scale (CCOS), a novel 16-point tool for evaluating outcome, to a consecutive series of CM1 patients to identify specific factors or symptoms that predispose to a better or worse surgical outcome. 2

Surgery is the definitive treatment option for symptomatic Chiari malformation I (CMI), but there is no clear consensus as to the preferred surgical method. 9 This study aimed to quantitatively assess and compare the effect and safety of dura splitting decompression (DSD) and posterior fossa decompression with duraplasty (PFDD) in treating patients with CMI. 9

The aim of this study was to prospectively compare the radiographic and clinical outcomes between the posterior fossa decompression (PFD) and PFD with duraplasty (PFDD) procedures in adolescent patients with Chiari malformation type I (CMI). 6

This study aimed to summarize the clinical features, diagnosis, and treatment of Chiari malformation type I- (CM-1-) associated syringobulbia. 8 We performed a literature review of CM-1-associated syringobulbia in PubMed, Ovid MEDLINE, and Web of Science databases. 8 Our concerns were the clinical features, radiologic presentations, treatment therapies, and prognoses of CM-1-associated syringobulbia. 8 This review identified 23 articles with 53 cases. 8 Symptoms included headache, neck pain, cranial nerve palsy, limb weakness/dysesthesia, Horner syndrome, ataxia, and respiratory disorders. 8 The most frequently involved area was the medulla. 8 Most of the patients also had syringomyelia. 8 Surgical procedures performed included posterior fossa decompression, foramen magnum decompression, cervical laminectomy, duraplasty, and syringobulbic cavity shunt. 8 Most patients experienced symptom alleviation or resolution postoperatively. 8 A syringobulbic cavity shunt provided good results in refractory cases. 8 Physicians should be aware of the possibility of syringobulbia in CM-1 patients, especially those with symptoms of sudden-onset brain-stem involvement. 8 The diagnosis relies on the disorder's specific symptomatology and magnetic resonance imaging. 8 Our review suggests that the initial therapy should be posterior fossa decomposition with or without duraplasty. 8 In refractory cases, additional syringobulbic cavity shunt is the preferred option. 8

Posterior fossa decompression without (PFD) or with duraplasty (PFDD) for the treatment of type 1 Chiari malformation (CM-1) is controversial. 7 We thus performed a systematic review and meta-analysis of studies to assess the effect on clinical and imaging improvement, operative time, complications, and recurrence rate between PFD and PFDD in patients with CM-1. 7

The treatment of Chiari malformation type 1 (CM-I) with posterior fossa decompression without (PFD) or with duraplasty (PFDD) is controversial. 4 Our aim is to compare the clinical outcome between the two methods for the treatment of CM-I. 4 In this paper, the authors report a systematic review and meta-analysis of operation time, clinical improvement, and complications of PFD compared with PFDD for the treatment of CM-I. 4 Randomized or non-randomized controlled trials of PFD and PFDD were considered for inclusion. 4 Twelve published reports of eligible studies involving 841participants meet the inclusion criteria. 4 There is significant difference in the operative time [mean difference = -74.63, 95 % CI (-83.02, -66.25), p < 0.05] in favor of PFD compared with PFDD. 4 There is significant difference in overall complication rates [mean difference = 0.34, 95 % CI (0.19, 0.60), p < 0.05] and rates of CSF leak [mean difference = 0.24, 95 % CI (0.07, 0.78), p < 0.05] in favor of PFD groups. 4 However, there is significant difference in the clinical improvement rate in favor of the PFDD group [mean difference = 0.85, 95 % CI (0.73, 0.99), p < 0.05]. 4 Although PFDD is related with longer operation time and higher CSF leak rate, it can still be considered as a preferable treatment option for most CM-I patients for its higher improvement rate. 4 More evidence from advanced multi-center studies are needed to provide illumination for the surgical decision making of CM-I. 4

Treatment summary

Treatment options for Chiari malformation type 1 include surgical decompression, duraplasty, and tonsillectomy. 5 , 12 , 10 Microvascular decompression and suboccipital decompression may also be performed. 11 Depending on the symptoms, a syringobulbic cavity shunt may also be a viable treatment option. 8

Benefits and Risks

Benefits summary

Treatment for Chiari malformation can improve or eliminate symptoms such as headache, neck pain, and limb weakness/dysesthesia. 8 , 4 It can also improve symptoms like hemifacial spasm. 11 Improved cerebrospinal fluid flow can potentially slow the progression of syringomyelia. 8

Risks summary

Treatment for Chiari malformation comes with the risks associated with surgery. 4 Post-operative complications may include cerebrospinal fluid leaks, infections, and nerve damage. 4 There is also a risk of symptom recurrence or new symptom development. 11 , 5 Certain treatment methods may involve longer operative times. 4

Comparison of Studies

Similarities between studies

Many studies show that surgery is an effective treatment method for Chiari malformation type 1. 4 , 7 , 10 , 1 It is also common across studies that surgery carries certain risks. 4 , 7 , 9

Differences between studies

There may be differences in the effectiveness of surgical methods and the extent of risks depending on the study. 9 For instance, there is a difference in clinical improvement rates and complication rates between posterior fossa decompression with duraplasty and dura splitting decompression. 9 Additionally, there may be variations in surgical indications and risks between children and adults. 1 , 12

Consistency and inconsistencies of results

The effectiveness of treatment methods for Chiari malformation type 1 differs depending on the study, and there is no clear consensus. 7 , 4 , 10 Furthermore, clinical improvement rates and complication rates may vary depending on the surgical method used. 9 , 4

Points to note for real-life application

When choosing a treatment method for Chiari malformation type 1, it is necessary to consider the patient's symptoms, medical history, and age. 3 , 5 It is also important to understand that surgery comes with risks. 4 , 7 , 9 It is crucial to discuss treatment options thoroughly with your doctor. 4 , 7

Limitations of current research

There are several limitations to Chiari malformation research, such as small sample sizes and a lack of multi-center studies. 4 , 7 It can also be difficult to compare results due to inconsistent research methods and evaluation methods. 3 Further research on Chiari malformation is needed. 4 , 7

Future research directions

Future research should evaluate the effectiveness and safety of treatment methods for Chiari malformation type 1 through larger, multi-center studies. 4 , 7 Standardizing research methods and evaluation methods will enable more accurate comparison of results. 3 Research focused on developing more effective treatment methods and preventive measures for Chiari malformation is also necessary. 5

Conclusion

Chiari malformation type 1 is a condition of the brain that can cause a variety of symptoms. 13 , 14 Surgery can be an effective treatment, but it is important to understand the associated risks. 4 , 7 , 9 When choosing a treatment method, it is important to consult with your doctor and support further research on Chiari malformation. 4 , 7

List of Treatments

• Posterior fossa decompression 7 , 4
• Duraplasty 7 , 4
• Tonsillectomy 12
• Microvascular decompression 11
• Syringobulbic cavity shunt 8