At the end of the nineteenth century, two pathologists, Julius Arnold (1835-1915) and Hans Chiari (1851-1916), described a complex clinical and pathological condition involving deformity of the cerebellum and brainstem, in children. Chiari malformations are now defined as a spectrum of hindbrain abnormalities involving the cerebellum, brainstem, skull base, and cervical cord. According to the type of herniation of the brain tissue displaced in the spinal canal, and the characteristics of the anomalies of the development of the brain or the spine, four types of Chiari malformations (types I to IV) are classified. Together with basilar invaginations, Chiari malformations represent the most common craniocervical junction malformations seen in adults.
Among Chiari malformations, Arnold-Chiari I malformation, otherwise known as the Chiari type I malformation, is the more common variant. It is characterized by the caudal descent of the cerebellar tonsils through the foramen magnum.[1] However, there is no accepted universal definition amongst clinicians as the malformation shows incongruity in clinic radiological correlation.[2] Some authors, for example, have recently proposed to define the Chiari type I malformation as 'Chiari syndrome,' while the term malformation should be reserved for types II-III.[3] Clinically, Chiari malformation type I can be asymptomatic ('hindbrain hernia') or manifests itself in late childhood or adulthood with tussive headaches and focal neurological manifestations. On the other hand, type II, III, and IV are congenital and clinically important. The nosographic collocation of type 0 or 0.5 Chiari malformation or 'Chiari like' (symptoms without tonsillar herniation), type 1.5 Chiari malformation (intermediate between type I and II), and complex Chiari is controversial and not universally accepted.
Chiari type I malformation can have a genetic basis or can be secondary to different conditions involving alterations in the basal skull such as craniosynostosis, craniocerebral disproportion, platybasia, secondary neurulation abnormalities, bone metabolic disorders. This type of malformation can be the result of a build-up of pressure in the brain produced, for instance, by hydrocephalus or a tumor. Furthermore, iatrogenic Chiari I, due to lumboperitoneal shunt for treatment of idiopathic intracranial hypertension has also been reported.[4] An injury-related Chiari I type is a rare but possible condition.
In some cases, it is also possible that a traction mechanism from below is the cause of the disease. According to a mechanisms of caudal traction (tethered cord), indeed, the lowering of the tonsils in Arnold Chiari type I could be provoked by a traction by the filum terminal (between the coccyx and the sacral part of the vertebral column), that pulls from the bone marrow and brainstem structures, causing, in turn, the descent of the cerebellar tonsils.[5]
When a genetic basis can be suggested, links to chromosomes 2, 9, 14, and 15 have been proposed.[6][7][8] For instance, a mutation in the NKX2-1 gene (14q13.3) that provides instructions for making the protein Nkx-2.1, a member of the homeobox protein family involved in the formation of body structures such as forebrain during early embryonic development, has been recently identified, in a girl affected by Chiari type I.[9] Another potential mutation can involve EPAS1 (2p21) encoding the hypoxia-inducible factor 2-alpha (HIF-2-alpha) that is the major regulator of erythropoietin and is implicated in the endochondral and intramembranous ossification.[10] These genetic disorders probably induce an impairment of the development of the para-axial mesoderm with herniation of the cerebellar tonsils, resulting in a small posterior fossa and crowded foramen magnum. This is consistent with a proposed association with other mesodermal connective tissue disorders, for example, Ehlers-Danlos syndrome [11], although the relationship between this condition and Chiari I is still unclear. Researchers from the Italian neurological Carlo Besta Institute, have recently dissected different pathways (e.g., disorders of the RAS/MAPK pathway) that can be found altered in both Chiari I malformation and defined genetic syndromes.[12] Despite these data, the genetics of the Chiari I malformation needs more confirmation.[13]
Chiari type I is the most common Chiari malformation. It is estimated to occur in approximately every 1 in 1000 births, with a slight female: male predominance of 1.3 to 1.[14] Probably, the epidemiological data is underestimated, since many forms are paucisymptomatic and manifest themselves clinically only in adulthood. Indeed, neuroimaging data suggest that the clinical condition may be more frequent, with an estimated prevalence of 1% in the pediatric population.[15][16]
Chiari malformation type I is described according to the morphology of the hindbrain. Classic features are a greater than 5 mm descent of the caudal tip of cerebellar tonsils past the foramen magnum; however, as little as less than 3 mm caudal cerebellar descent may be seen in a child presenting early with Chiari I.[17][18][19][20] Of note, there is no an associated herniation of the brainstem and spina bifida that characterize Chiari type II, or classic Chiari malformation; severe protrusion or herniation of the cerebellum and brainstem involving serious consequences on the development of the nervous system (type III); or incomplete or undeveloped cerebellum with structural alterations of the skull and spinal cord (type IV).
In Chiari type I, the main cause of pathology is due to tonsillar invagination and direct compression of neurological structures within the foramen magnum/upper spinal cord, with obstruction of cerebrospinal fluid (CSF) and potentially associated syringomyelia. This latter malformation, also termed as Morvan disease, is myelopathy that consists of the abnormal formation of one or more cysts or cavities (syrinxes) containing CSF inside the spinal cord and is detectable in 20% to 85% of Chiari I cases. Secondary features by way of syrinx formation may be further obstruction of spinal canal CSF outflow and further direct compression of neurovascular structures.[21] Regarding the location of syringomyelia development, the most common region affected is the cervical region, followed by combined cervical and thoracic syringomyelia. The pathogenesis of syringomyelia must be well elucidated. A theory postulates the role of arterial pulsation that could induce a pressure dissociation between the subarachnoid spaces of the cranium and spinal cord. Again, other theories suggest that syrinx may represent the effect of the anatomical defect of the cerebellar tonsils or the consequence of the altered CSF flow.[22] Syringobulbia that communicates with the fourth ventricle has also been described.[23]
Because the foramen of Magendie can be obstructed, the fourth ventricle can result enlarged. Hydrocephalus may occur in approximately 10% of patients. Skeletal associations may include platybasia/basilar invagination, Sprengel deformity, and atlantooccipital assimilation. Syndromic associations include Klippel-Feil, Gorham-Stout disease, Crouzon, and Pfeiffer syndromes.[18] Many of these conditions involve alterations of the basal skull and may themselves be causes of the Chiari malformation.
Patients with Chiari I malformation are asymptomatic. The most common symptom, however, in both the adult and child, is pain or headache in the occipital/cervical region (neck pain) [24]. In the very young population, a history of headache or pain may be difficult to elicit, where these symptoms are more likely to manifest as excessive crying, irritability, and failure to thrive.[19][25]
It should be noted that the headache produced in Chiari I is often exacerbated with the Valsalva maneuver due to the reduced size of the foramen magnum. This should be differentiated from chronic headaches that do not vary with the Valsalva maneuver, which may be attributed to pathologies other than Chiari I, for example, intracranial hypertension.[26][27] Although migraine headaches have a prevalence similar to that of the general population, in individuals affected by Chiari I there is an earlier age of onset and a severe clinical presentation.[28]
Apart from headache and pain, a wide spectrum of clinical manifestations may characterize the malformation. In particular, signs and symptoms are mainly due to direct brainstem compression that may cause autonomic dysfunction.[29][30] Other signs, such as scoliosis, are structural. Clinical features may include[29][30][31][24][32][33][34]:
Adults and children may present with Chiari I differently. For example, pediatric patients are increasingly likely to present with brainstem dysfunction, sleep apnea, or feeding difficulty.[35] The latter is due to the involvement of the glossopharyngeal and vagus nerves resulting in an absent gag reflex and hoarseness.[36] As the cerebellum is involved in higher cognitive functions, potential cognitive alterations have been recently investigated, and the presence of a generalized cognitive impairment in the executive functioning, verbal fluency, spatial cognition, language, and memory processing, has been reported.[37]
Neuroimaging
Magnetic resonance imaging (MRI) is the main investigation performed for Chiari type I malformation, providing a depiction of craniocervical junction anatomy with identification of secondary complications such as hydrocephalus or syringomyelia.[38]
When the patient is unable to undergo MRI scanning, other methods investigations to explore include CT myelography, non-contrast CT, and radiographs of the head and neck.
On MRI, as well as tonsillar descent, there may be an appearance of ‘peg-like’ or pointed tonsils, seen in both symptomatic and asymptomatic individuals.[39] Other associations include a cervicomedullary ‘kink,’ seen in up to 71% of symptomatic patients.[40] In general, the greater the degree of cerebellar tonsil descent, the greater the likelihood the patient is symptomatic.[18]
Patients who have incidental tonsillar ectopia without symptoms may benefit from MRI cine CSF flow studies. Positive findings on CSF flow include pulsatile systolic tonsillar descent and CSF flow obstruction at the level of the foramen magnum. These findings can provide further information to help assess whether the patient may benefit from surgery.[41]
Laboratory Studies
Laboratory studies are not used for the diagnosis of Chiari I. However, any preoperative workup requires appropriate baseline investigations including full blood counts, electrolytes and metabolites; alongside a chest radiograph and electrocardiogram (ECG).
Other useful tests may include:
Sleep study: Involves sleeping overnight in a room where they can monitor breathing, snoring, oxygenation, and seizure activity to determine if there is any evidence of sleep apnea.
Swallowing study: Fluoroscopy used to watch the internal swallowing process to determine if there is an abnormality suggestive of lower brainstem dysfunction.
Brainstem auditory evoked potential (BAER): It is an electrical test to examine the function of the hearing apparatus and brainstem connections. This is used to determine if the brainstem is working properly.
Prenatal diagnosis of Chiari type I malformation, and syringomyelia has also been described.[42]
Because there is no clear consensus about the precise algorithm for the management of Chiari type I malformation, its treatment remains rather empirical. It encompasses a combination of medical and surgical approaches through a multimodal dynamic strategy.
Medical therapy
Medical management in Chiari I is limited and generally confined to symptomatology (e.g., headaches or neck pain). Non-steroidal anti-inflammatory drugs (NSAIDs), muscle relaxants, and physical support collars may provide symptomatic relief. However, these options provide little improvement of less common symptoms, for example, gait disturbance. Meditation, yoga, or mindfulness therapy have also been proposed for addressing pain.
Surgical strategies
Surgical treatment is typically reserved for patients who present with severe or worsening symptoms who go on to have a confirmation of cerebellar descent on imaging and a Chiari malformation obstructing CSF flow confirmed by cine MRI. Surgery aims to provide decompression of the restricted cervicomedullary junction, allowing CSF flow to be restored to optimal levels. The main approach involves performing a suboccipital craniectomy at the level of the C1 posterior arch (C1/2 laminectomy), with or without associated duroplasty.[43] Thus, this intervention, indicated as posterior fossa decompression (PFD), is the most adopted neurosurgical approach focused on restoring CSF flow across the foramen magnum. The procedure is performed in up to 99% of the literature.[44] A minimally invasive procedure allowing resection of submeningeal cerebellar tonsillar herniation followed by reconstruction of Cisterna magna without craniectomy has been proposed for addressing Chiari I with syringomyelia.[45] Of note, cine MRI has been proposed for guiding the intraoperative decision to realize duraplasty during PFD.[46] Among non-invasive approaches, several methods have also been proposed to decompress syringomyelia with distal drainage to the subarachnoid space (syringosubarachnoid shunt).[47]
Important diagnoses to consider in the workup of Chiari I are:
The most common postoperative complications are CSF leakage and pseudomeningocele formation.[50][24] The latter may require revision surgery or shunt insertion.[51] Other complications include aseptic and bacterial meningitis, vertebral artery injury, and epidural hematoma formation.[52] Concerning the type of surgical approach, in a retrospective analysis, Farber et al. found that meningitis occurred especially in decompression and duraplasty performed using bovine pericardial xenograft compared with the allograft method.[53]
Postoperatively patients may experience headache and neck pain due to the operation. Neck exercises may be given to aid the return of full mobility as soon as it is able.
Patients typically return to work in 4 to 6 weeks, with a follow-up MRI performed at around 6 months to 1 year.
Full recovery from Chiari surgery may take months or longer. It is important to slowly increase activity in a graded manner, avoiding any strenuous lifting in the early phase of recovery.
While nothing can be done to prevent congenital Chiari type I malformation, patient education plays a large role in familiarising not only the patient about the signs and symptoms of the condition but also helping increase awareness of the close family, friends, and carers who may spend significant periods with the patient.
The Chiari type I malformation is a rare developmental disorder that is best managed by an interprofessional team that includes a neurologist, pediatrician, surgeon, social worker, nurse, and physical therapist. These patients tend to have many physical and functional limitations, including impairment of swallowing, speaking, and even walking.
While the prognosis for most patients is good, when clinically suspected, appropriate investigations should be performed promptly to facilitate an appropriate level of treatment (e.g.conservative vs. surgical) and, in turn, to prevent future deterioration.
[1] | Abd-El-Barr MM,Strong CI,Groff MW, Chiari malformations: diagnosis, treatments and failures. Journal of neurosurgical sciences. 2014 Dec; [PubMed PMID: 25418275] |
[2] | Muzumdar D, Chiari 1 malformation: Revisited. Journal of pediatric neurosciences. 2019 Oct-Dec [PubMed PMID: 31908657] |
[3] | Frič R,Eide PK, Chiari type 1-a malformation or a syndrome? A critical review. Acta neurochirurgica. 2019 Oct 28 [PubMed PMID: 31656982] |
[4] | Hentati A,Badri M,Bahri K,Zammel I, Acquired Chiari I malformation due to lumboperitoneal shunt: A case report and review of literature. Surgical neurology international. 2019 [PubMed PMID: 31528416] |
[5] | Yan H,Han X,Jin M,Liu Z,Xie D,Sha S,Qiu Y,Zhu Z, Morphometric features of posterior cranial fossa are different between Chiari I malformation with and without syringomyelia. European spine journal : official publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society. 2016 Jul [PubMed PMID: 26821142] |
[6] | Speer MC,George TM,Enterline DS,Franklin A,Wolpert CM,Milhorat TH, A genetic hypothesis for Chiari I malformation with or without syringomyelia. Neurosurgical focus. 2000 Mar 15; [PubMed PMID: 16676924] |
[7] | Abbott D,Brockmeyer D,Neklason DW,Teerlink C,Cannon-Albright LA, Population-based description of familial clustering of Chiari malformation Type I. Journal of neurosurgery. 2018 Feb; [PubMed PMID: 28156254] |
[8] | Boyles AL,Enterline DS,Hammock PH,Siegel DG,Slifer SH,Mehltretter L,Gilbert JR,Hu-Lince D,Stephan D,Batzdorf U,Benzel E,Ellenbogen R,Green BA,Kula R,Menezes A,Mueller D,Oro' JJ,Iskandar BJ,George TM,Milhorat TH,Speer MC, Phenotypic definition of Chiari type I malformation coupled with high-density SNP genome screen shows significant evidence for linkage to regions on chromosomes 9 and 15. American journal of medical genetics. Part A. 2006 Dec 15; [PubMed PMID: 17103432] |
[9] | Gonçalves D,Lourenço L,Guardiano M,Castro-Correia C,Sampaio M,Leão M, Chiari Malformation Type I in a Patient with a Novel {i}NKX2-1{/i} Mutation. Journal of pediatric neurosciences. 2019 Jul-Sep [PubMed PMID: 31649781] |
[10] | Rosenblum JS,Maggio D,Pang Y,Nazari MA,Gonzales MK,Lechan RM,Smirniotopoulos JG,Zhuang Z,Pacak K,Heiss JD, Chiari Malformation Type 1 in {i}EPAS1{/i}-Associated Syndrome. International journal of molecular sciences. 2019 Jun 10 [PubMed PMID: 31185588] |
[11] | Milhorat TH,Bolognese PA,Nishikawa M,McDonnell NB,Francomano CA, Syndrome of occipitoatlantoaxial hypermobility, cranial settling, and chiari malformation type I in patients with hereditary disorders of connective tissue. Journal of neurosurgery. Spine. 2007 Dec; [PubMed PMID: 18074684] |
[12] | Saletti V,Viganò I,Melloni G,Pantaleoni C,Vetrano IG,Valentini LG, Chiari I malformation in defined genetic syndromes in children: are there common pathways? Child's nervous system : ChNS : official journal of the International Society for Pediatric Neurosurgery. 2019 Oct [PubMed PMID: 31363831] |
[13] | Capra V,Iacomino M,Accogli A,Pavanello M,Zara F,Cama A,De Marco P, Chiari malformation type I: what information from the genetics? Child's nervous system : ChNS : official journal of the International Society for Pediatric Neurosurgery. 2019 Oct [PubMed PMID: 31385087] |
[14] | Langridge B,Phillips E,Choi D, Chiari Malformation Type 1: A Systematic Review of Natural History and Conservative Management. World neurosurgery. 2017 Aug; [PubMed PMID: 28435116] |
[15] | Pertl B,Eder S,Stern C,Verheyen S, The Fetal Posterior Fossa on Prenatal Ultrasound Imaging: Normal Longitudinal Development and Posterior Fossa Anomalies. Ultraschall in der Medizin (Stuttgart, Germany : 1980). 2019 Dec [PubMed PMID: 31794996] |
[16] | Aitken LA,Lindan CE,Sidney S,Gupta N,Barkovich AJ,Sorel M,Wu YW, Chiari type I malformation in a pediatric population. Pediatric neurology. 2009 Jun [PubMed PMID: 19433279] |
[17] | Hidalgo JA,Varacallo M, Arnold Chiari Malformation 2019 Jan; [PubMed PMID: 28613730] |
[18] | Elster AD,Chen MY, Chiari I malformations: clinical and radiologic reappraisal. Radiology. 1992 May; [PubMed PMID: 1561334] |
[19] | Tubbs RS,Lyerly MJ,Loukas M,Shoja MM,Oakes WJ, The pediatric Chiari I malformation: a review. Child's nervous system : ChNS : official journal of the International Society for Pediatric Neurosurgery. 2007 Nov; [PubMed PMID: 17639419] |
[20] | Barkovich AJ,Wippold FJ,Sherman JL,Citrin CM, Significance of cerebellar tonsillar position on MR. AJNR. American journal of neuroradiology. 1986 Sep-Oct; [PubMed PMID: 3096099] |
[21] | Dlouhy BJ,Dawson JD,Menezes AH, Intradural pathology and pathophysiology associated with Chiari I malformation in children and adults with and without syringomyelia. Journal of neurosurgery. Pediatrics. 2017 Dec; [PubMed PMID: 29027876] |
[22] | Koyanagi I,Houkin K, Pathogenesis of syringomyelia associated with Chiari type 1 malformation: review of evidences and proposal of a new hypothesis. Neurosurgical review. 2010 Jul [PubMed PMID: 20532585] |
[23] | Menezes AH,Greenlee JDW,Dlouhy BJ, Syringobulbia in pediatric patients with Chiari malformation type I. Journal of neurosurgery. Pediatrics. 2018 Jul [PubMed PMID: 29701558] |
[24] | Tubbs RS,Beckman J,Naftel RP,Chern JJ,Wellons JC 3rd,Rozzelle CJ,Blount JP,Oakes WJ, Institutional experience with 500 cases of surgically treated pediatric Chiari malformation Type I. Journal of neurosurgery. Pediatrics. 2011 Mar; [PubMed PMID: 21361762] |
[25] | Listernick R,Tomita T, Persistent crying in infancy as a presentation of Chiari type I malformation. The Journal of pediatrics. 1991 Apr; [PubMed PMID: 2007932] |
[26] | McGirt MJ,Nimjee SM,Floyd J,Bulsara KR,George TM, Correlation of cerebrospinal fluid flow dynamics and headache in Chiari I malformation. Neurosurgery. 2005 Apr; [PubMed PMID: 15792510] |
[27] | Chiapparini L,Saletti V,Solero CL,Bruzzone MG,Valentini LG, Neuroradiological diagnosis of Chiari malformations. Neurological sciences : official journal of the Italian Neurological Society and of the Italian Society of Clinical Neurophysiology. 2011 Dec; [PubMed PMID: 21800079] |
[28] | Jokonya L,Makarawo S,Mduluza-Jokonya TL,Ngwende G, Fatal status migrainosus in Chiari 1 malformation. Surgical neurology international. 2019 [PubMed PMID: 31893144] |
[29] | Weig SG,Buckthal PE,Choi SK,Zellem RT, Recurrent syncope as the presenting symptom of Arnold-Chiari malformation. Neurology. 1991 Oct; [PubMed PMID: 1922816] |
[30] | Selmi F,Davies KG,Weeks RD, Type I Chiari deformity presenting with profound sinus bradycardia: case report and literature review. British journal of neurosurgery. 1995; [PubMed PMID: 7576283] |
[31] | Schneider B,Birthi P,Salles S, Arnold-Chiari 1 malformation type 1 with syringohydromyelia presenting as acute tetraparesis: a case report. The journal of spinal cord medicine. 2013 Mar [PubMed PMID: 23809533] |
[32] | Tubbs RS,Doyle S,Conklin M,Oakes WJ, Scoliosis in a child with Chiari I malformation and the absence of syringomyelia: case report and a review of the literature. Child's nervous system : ChNS : official journal of the International Society for Pediatric Neurosurgery. 2006 Oct; [PubMed PMID: 16532361] |
[33] | Strahle JM,Taiwo R,Averill C,Torner J,Shannon CN,Bonfield CM,Tuite GF,Bethel-Anderson T,Rutlin J,Brockmeyer DL,Wellons JC,Leonard JR,Mangano FT,Johnston JM,Shah MN,Iskandar BJ,Tyler-Kabara EC,Daniels DJ,Jackson EM,Grant GA,Couture DE,Adelson PD,Alden TD,Aldana PR,Anderson RCE,Selden NR,Baird LC,Bierbrauer K,Chern JJ,Whitehead WE,Ellenbogen RG,Fuchs HE,Guillaume DJ,Hankinson TC,Iantosca MR,Oakes WJ,Keating RF,Khan NR,Muhlbauer MS,McComb JG,Menezes AH,Ragheb J,Smith JL,Maher CO,Greene S,Kelly M,O'Neill BR,Krieger MD,Tamber M,Durham SR,Olavarria G,Stone SSD,Kaufman BA,Heuer GG,Bauer DF,Albert G,Greenfield JP,Wait SD,Van Poppel MD,Eskandari R,Mapstone T,Shimony JS,Dacey RG,Smyth MD,Park TS,Limbrick DD, Radiological and clinical predictors of scoliosis in patients with Chiari malformation type I and spinal cord syrinx from the Park-Reeves Syringomyelia Research Consortium. Journal of neurosurgery. Pediatrics. 2019 Aug 16 [PubMed PMID: 31419800] |
[34] | Dobkin BH, The adult Chiari malformation. Bulletin of the Los Angeles neurological societies. 1977 Mar; [PubMed PMID: 610783] |
[35] | Greenlee JD,Donovan KA,Hasan DM,Menezes AH, Chiari I malformation in the very young child: the spectrum of presentations and experience in 31 children under age 6 years. Pediatrics. 2002 Dec; [PubMed PMID: 12456921] |
[36] | Dyste GN,Menezes AH,VanGilder JC, Symptomatic Chiari malformations. An analysis of presentation, management, and long-term outcome. Journal of neurosurgery. 1989 Aug; [PubMed PMID: 2746341] |
[37] | García M,Lázaro E,López-Paz JF,Martínez O,Pérez M,Berrocoso S,Al-Rashaida M,Amayra I, Cognitive Functioning in Chiari Malformation Type I Without Posterior Fossa Surgery. Cerebellum (London, England). 2018 Oct [PubMed PMID: 29766459] |
[38] | McVige JW,Leonardo J, Neuroimaging and the clinical manifestations of Chiari Malformation Type I (CMI). Current pain and headache reports. 2015 Jun; [PubMed PMID: 26017710] |
[39] | Aboulezz AO,Sartor K,Geyer CA,Gado MH, Position of cerebellar tonsils in the normal population and in patients with Chiari malformation: a quantitative approach with MR imaging. Journal of computer assisted tomography. 1985 Nov-Dec; [PubMed PMID: 4056132] |
[40] | Spinos E,Laster DW,Moody DM,Ball MR,Witcofski RL,Kelly DL Jr, MR evaluation of Chiari I malformations at 0.15 T. AJR. American journal of roentgenology. 1985 Jun; [PubMed PMID: 3873794] |
[41] | Hofkes SK,Iskandar BJ,Turski PA,Gentry LR,McCue JB,Haughton VM, Differentiation between symptomatic Chiari I malformation and asymptomatic tonsilar ectopia by using cerebrospinal fluid flow imaging: initial estimate of imaging accuracy. Radiology. 2007 Nov; [PubMed PMID: 17890352] |
[42] | Iruretagoyena JI,Trampe B,Shah D, Prenatal diagnosis of Chiari malformation with syringomyelia in the second trimester. The journal of maternal-fetal & neonatal medicine : the official journal of the European Association of Perinatal Medicine, the Federation of Asia and Oceania Perinatal Societies, the International Society of Perinatal Obstetricians. 2010 Feb [PubMed PMID: 19572237] |
[43] | Siasios J,Kapsalaki EZ,Fountas KN, Surgical management of patients with Chiari I malformation. International journal of pediatrics. 2012; [PubMed PMID: 22811732] |
[44] | Arnautovic A,Splavski B,Boop FA,Arnautovic KI, Pediatric and adult Chiari malformation Type I surgical series 1965-2013: a review of demographics, operative treatment, and outcomes. Journal of neurosurgery. Pediatrics. 2015 Feb [PubMed PMID: 25479580] |
[45] | Lou Y,Yang J,Wang L,Chen X,Xin X,Liu Y, The clinical efficacy study of treatment to Chiari malformation type I with syringomyelia under the minimally invasive surgery of resection of Submeningeal cerebellar Tonsillar Herniation and reconstruction of Cisterna magna. Saudi journal of biological sciences. 2019 Dec [PubMed PMID: 31885484] |
[46] | Delavari N,Wang AC,Bapuraj JR,Londy F,Muraszko KM,Garton HJL,Maher CO, Intraoperative Phase Contrast MRI Analysis of Cerebrospinal Fluid Velocities During Posterior Fossa Decompression for Chiari I Malformation. Journal of magnetic resonance imaging : JMRI. 2020 May [PubMed PMID: 31667928] |
[47] | Amarouche M,Minichini V,Davis H,Giamouriadis A,Bassi S, Syringosubarachnoid shunt: insertion technique. British journal of neurosurgery. 2019 Dec 18 [PubMed PMID: 31852253] |
[48] | Greenberg JK,Yarbrough CK,Radmanesh A,Godzik J,Yu M,Jeffe DB,Smyth MD,Park TS,Piccirillo JF,Limbrick DD, The Chiari Severity Index: a preoperative grading system for Chiari malformation type 1. Neurosurgery. 2015 Mar; [PubMed PMID: 25584956] |
[49] | De Vlieger J,Dejaegher J,Van Calenbergh F, Multidimensional, patient-reported outcome after posterior fossa decompression in 79 patients with Chiari malformation type I. Surgical neurology international. 2019 [PubMed PMID: 31893143] |
[50] | Rocque BG,Oakes WJ, Surgical Treatment of Chiari I Malformation. Neurosurgery clinics of North America. 2015 Oct; [PubMed PMID: 26408062] |
[51] | Lei ZW,Wu SQ,Zhang Z,Han Y,Wang JW,Li F,Shu K, Clinical Characteristics, Imaging Findings and Surgical Outcomes of Chiari Malformation Type I in Pediatric and Adult Patients. Current medical science. 2018 Apr; [PubMed PMID: 30074187] |
[52] | Tubbs RS,Smyth MD,Wellons JC 3rd,Oakes WJ, Distances from the atlantal segment of the vertebral artery to the midline in children. Pediatric neurosurgery. 2003 Dec; [PubMed PMID: 14734868] |
[53] | Farber H,McDowell MM,Alhourani A,Agarwal N,Friedlander RM, Duraplasty Type as a Predictor of Meningitis and Shunting After Chiari I Decompression. World neurosurgery. 2018 Oct [PubMed PMID: 30026145] |