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For citation purposes: Choudhury PR, Sarda P, Baruah P, Singh S. Congenital Chiari malformations: Magnetic resonance imaging study. OA Case Reports 2013 Aug 08;2(8):73.

Research study

 
Radiology

A magnetic resonance imaging study of congenital Chiari malformations

PR Choudhury1*, P Sarda2, P Baruah1, S Singh3
 

Authors affiliations

(1) Department of Anatomy, Fakhruddin Ali Ahmed Medical College, Barpeta, Assam, India

(2) Department of Radiology, Gauhati Medical College, Guwahati, Assam, India

(3) Department of Radiology, B. Borooah Cancer Institute, Gopinath Nagar, Guwahati, Assam, India

*Corresponding author Emails: prcanatomist@gmail.com; prabahitabaruah@gmail.com

Abstract

Introduction

Chiari malformations are developmental anomalies with the herniation of the brainstem medulla and the cerebellar tonsils and vermis through the foramen magnum. The patients manifest with headache, neck pain, progressive scoliosis and cerebellar dysfunction due to cervico-medullary compression. These malformations range from the simpler to the more complex varieties of presentation, signifying their stages of appearance during embryological differentiation and development. The aim was to study various types of Chiari malformations with the help of magnetic resonance imaging techniques.

Materials and methods

In this study, 45 cases of Chiari malformations were considered.

Results

Among 45 cases, 37, 6 and 2 were type 1, 2 and 3 Chiari malformations, respectively. 53.33% cases were male and rest were female cases. The hydrocephalus and syringomyelia were present in 28.89% and 48.89% of cases, respectively. Length of herniated cerebeller tonsil in 56.76% cases of type 1 Chiari malformations are in between 10 mm and less than 20 mm.

Conclusion

The magnetic resonance imaging technique gives better visualisation of Chiari malformations and thus this entity has rapidly evolved over the past decade.

Introduction

A complex range of anomalies of the hindbrain formation appearing at various stages of growth and development of the central nervous system are included under the group called Chiari malformations.Chiari malformation is the most common anomaly of the craniovertebral junction involving both the skeletal as well as the neural structures[1].

Professor Chiari first described the abnormalities that we now refer to as Chiari malformations around 1890. His observations were all made on stillborn babies or newborns, and he classified the abnormalities by the severity of tonsillar and cerebellar descent as type 1 being the least and type 4 the most severe[2].

The incidence of Chiari type 1 malformation by neuroimaging techniques range from 0.1 to 1%[3] and it is least obvious clinically and may not be diagnosed until adult life. It consists of tonsillar herniation through the foramen magnum with or without varying degrees of elongation of the medulla oblongata and fourth ventricle. Chiari type 2 is virtually always with thoracolumbar myelomeningocele and associated with caudal herniation of medulla, vermis and the fourth ventricle[4]. Chiari types 3 and 4 have the major deformities with cerebellar hypoplasia and downward displacement of the brain stem and a high cervical or occipital encephalocele[4].

Today, we have a much clearer understanding of these conditions due to the advent of magnetic resonance imaging (MRI) scanning[2]. As a result, this entity has rapidly evolved over the past decade with newer visualisation techniques, thus posing new challenges to diagnosis and management[1]. The aim of this workwas to study an MRI study of congenital Chiari malformations.

Materials and methods

The study is based on the cases referred to the Department of Radiology for MRI from Departments of Neurology and Paediatric surgery with common symptoms of headache, swallowing problems, dizziness, nystagmus, etc. Informed consent of the patients and their attendants were taken. The study was approved by the Institutional Ethics Committee of the Medical College and Hospital, where the study was carried out.

Altogether 45 cases were considered for the study. The cases were classified into three groups as ‘A’, ‘B’ and ‘C’, according to Chiari type 1, 2 and 3, respectively (shown in Table 1).

Table 1

Different types of Chiari malformations with their number and percentage

The readings and evaluations were made by professors, demonstrators and postgraduate trainees of Department of Radiology and Anatomy with 3–10 years of experience. The study was conducted from January 2008 to December 2012.

The data obtained from the MRI studies of 45 cases were tabulated, compared and calculated. The relative frequencies were calculated and p value was evaluated with the help of Student’s t-test probabilities.

Results

There were 24 males with a percentage of 53.33 out of 45 total cases and the rest were female. Distributions of male and female in different groups A, B and C (Figure 1)with percentages, mean, standard deviations and standard error of mean are shown in Table 2.

Table 2

Number and percentage of male and female cases for groups‘A’,‘B’and‘C’

Different types of Chiari malformations according to sex.

It can be concluded from Table 3 and Figure 2 that the maximum number of cases in groups A and B are in between the age groups of 15 years to less than 20 years and less than 5 years, respectively.

Table 3

Number of cases in different ages for the groups A, B and C

Different types of Chiari malformations in different age groups.

Relative frequency of Chiari malformations in between groups ‘A’, ‘B’ and ‘C’ can be studied from Table 4 and Figure 3.

Table 4

Distribution of frequency and relative frequency of Chiari malformations in groups ‘A’, ‘B’ and ‘C’

Relative frequency of groups ‘A’, ‘B’ and ‘C’.

The hydrocephalus and syringomyelia (syringomyelia shown in Figure 4) are present in 28.89% (13 out of 45 cases) and 48.89% (22 out of 45 cases) of cases, respectively, which can be concluded from Table 5. Lumbosacral meningomyelocele is found to be present in all the cases of type 2 Chiari malformations.

Table 5

Presence and absence of hydrocephalus and syringomyelia in groups ‘A’, ‘B’ and ‘C’

Magnetic resonance imaging showing tonsiller herniation (indicated by red arrow) and syringomyelia (indicated by white arrow).

Length of herniated cerebeller tonsil (shown in Figure 4) in 56.76% (21 out of 37 cases) cases of type 1 Chiari malformations are in between 10 and less than 20 mm (Table 6). The smallest length of cerebeller tonsil in type I Chiari malformation is 5.2 mm and longest being 28 mm.

Table 6

Length of herniated cerebeller tonsils in type 1 Chiari malformations

The level of significance of differences of Chiari malformations between male and females is not significant (p = <0.05) whereas that of groups A and B, and groups A and C according to age groups is very significant (p = <0.01) and very highly significant (p = <0.001), respectively (Table 7).

Table 7

The level of significance of differences of Chiari malformations in different groups

Discussion

Arnold–Chiari malformation is a complex syndrome in which the brainstem medulla, and the cerebellar tonsils and vermis herniate throughout the foramen magnum[5].

The Chiari malformation is classified into four types. Type 1 is the most commonly seen clinical entity and characterised by tonsillar herniation greater than 5 mm below the formen magnum. Syringomyelia is common with type 1 Chiari malformations[1]. In this study, 82.22% cases fall into type 1 category which also contains the maximum number of syringomyelia cases (Table 5).

Type 2 Chiari malformation is characterised by caudal descent of cerebellar vermis along with the brainstem and fourth ventricle. This type of Chiari malformation is associated with myelomeningocele. Presence of hydrocephalus is a common finding in this type[1]. In this study, 50% cases of type 2 is associated with hydrocephalus (Table 5). Type 3 is the rarest and most severe form, characterised by occipital or high cervical encephalocele containing herniated cerebellar or brainstem tissue. Marked cerebeller hypoplasia or aplasia is the main feature of type 4 Chiari malformation[1].

A discussion of the modern theories describing the aetiology of the congenital Chiari malformations begins with Gardner’s work[6]. The ‘hydrodynamic theory’ relates the development of tonsillar herniation and other dysraphic states to disordered embryogenesis in and around the foetal hindbrain. The initial insult is the failure of pathways for cerebrospinal fluid egress from the embryological fourth ventricle to open normally at the foramina of Luschka and Magendie. This blockage at the normal exits of the fourth ventricle results in increased pressure. The cerebellar tonsils migrate caudally in response to this pressure gradient, causing the hallmark finding of crowding of the foramen magnum. This elevated pressure can also be transmitted through the obex to the spinal cord and continued pressure allows for persistence or dilatation of the central canal of the spinal cord, resulting in the formation of hvdromyelic cavity[7].

According to Alden et al.[8], the exact origin of Chiari type 1 malformation is unknown; however, it appears to be caused by a mismatch between the volume of the posterior fossa neural elements and the posterior fossa cranial content. Several theories have been proposed to describe the resultant pathophysiology of this mismatch. It is clear, however, that abnormal cerebrospinal fluid flow and velocity play a role in the symptoms and signs associated with this disorder[8].

The common symptoms related to Chiari malformation are headache, particularly precipitated by coughing, straining, sneezing, etc. (Valsalva maneuvers), dizziness, eye symptoms, most commonly nystagmus, swallowing problems, and sleep disturbances[2].

Type 1 Chiari malformations has been described in association with many different genetic disorders of established inheritance patterns, including Klippel–Feil syndrome, Carpenter syndrome and Hadju–Cheney syndrome. But syndromic type 1 Chiari malformations accounts for less than 1% of prevalence of type Chiari malformations, with most occurring as isolated phenomena[9].

Conclusion

MRI has become the imaging technique of choice to diagnose Chiari malformations. It is accurate, specific and noninvasive. In the exceptional case when MRI cannot be performed, computed tomography-myelography/cisternography with formatted reconstructions can provide sufficient diagnostic information. In a number of cases, MRI alone may not be sufficient to clearly define the anatomy at the skull base or bony abnormalities in the cervical spine. The combination of MRI and reformatted computed tomography can define accurately the surgical anatomy and aid in surgical planning.

Authors Contribution

All authors contributed to the conception, design, and preparation of the manuscript, as well as read and approved the final manuscript.

Competing interests

None declared.

Conflict of interests

None declared.

A.M.E

All authors abide by the Association for Medical Ethics (AME) ethical rules of disclosure.

References

  • 1. Vannemreddy P, Nourbakhsh A, Willis B, Guthikonda B. Congenital Chiari malformations. J Neurol Soc India 2010 Mar;58(1):6-14.
  • 2. Batzdorf U . Chiari I malformation with syringomyelia. Evaluation of surgical therapy by magnetic resonance imaging. J Neurosurg 1988May;68(5):726-30.
  • 3. Meadows J, Kraut M, Guarnieri M, Haroun RI, Carson BS. Asymptomatic Chiari type I malformations identified on magnetic resonance imaging. J Neurosurg 2000 Jun;92(6):920-6.
  • 4. Sutton D, Stevens J, Miszkiel K, . Intracranial lesions (1). Text book of radiology and imaging 7th ed Noida, U.P (India): Elsevier 2009p1728.
  • 5. Zollty P, Sanders MH, Pollack IF. Chiari malformation and sleep-disorder breathing: a review of diagnostic management issues. Sleep 2000 Aug;23(5):637-43.
  • 6. Gardner WJ . Hydrodynamic mechanism of syringomyelia: its relationship to myelocele. J Neurol Neurosurg Psychiatry 1965 June;28(3):247-59.
  • 7. Jacob RP, Rhoton AL. The chiari I malformation. In: Anson JA, Benzel EC, Awad IA, editors. Syringomyelia and the chiari malformations. South Washington street,Park Ridge, IL: AANS Publication Committee 1997p58.
  • 8. Alden TD, Ojemann JG, Park TS. Surgical treatment of Chiari I malformation: indications and approaches. J Neurosurg 2001 Jul;11(1):1-5.
  • 9. Speer MC, George TM, Enterline DS, Franklin A, Wolpert CM, Milhorat TH. A genetic hypothesis for Chiari I malformation with or without syringomyelia. Neurosurg Focus 2000 Mar;8(3):E12.
Licensee to OAPL (UK) 2013. Creative Commons Attribution License (CC-BY)

Different types of Chiari malformations with their number and percentage

Groups Number of cases Percentage (out of 45)
Group A 37 82.22
Group B 6 13.33
Group C 2 4.45
Total 45 100

Number and percentage of male and female cases for groups‘A’,‘B’and‘C’

Groups Male Female
Number of cases Percentage (out of 24) Number of cases Percentage (out of 21)
Group A 20 83.33 17 80.95
Group B 3 12.5 3 14.29
Group C 1 4.17 1 4.76
Sum 24 100 21 100
Mean 8 33.33 7 33.33
SD ±10.44 ±43.498 ±8.718 ±41.512
SEM ±6.028 ±25.114 ±5.033 ±23.967

SD, standard deviation; SEM, standard error of mean

Number of cases in different ages for the groups A, B and C

Age groups (years) Groups
Group A Group B Group C
Less than 5 2 5 1
5 to <10 5 0 1
10 to <15 6 0 0
15 to <20 7 0 0
20 to <25 6 0 0
25 to <30 5 0 0
30 to <35 4 0 0
35 to <40 2 0 0
40 and above 0 1 0
Sum 37 6 2
Mean 4.11 0.667 0.222
SD ±2.315 ±1.658 ±0.4410
SEM ±0.7718 ±0.5528 ±0.1470

SD, standard deviation; SEM, standard error of mean

Distribution of frequency and relative frequency of Chiari malformations in groups ‘A’, ‘B’ and ‘C’

Class interval (years) Group A Group B Group C
Simple frequency (f) Relative frequency (fr) Simple frequency (f) Relative frequency (fr) Simple frequency (f) Relative frequency (fr)
Less than 5 2 0.054 5 0.833 1 0.5
5 to <10 5 0.136 0 0 1 0.5
10 to <15 6 0.162 0 0 0 0
15 to <20 7 0.189 0 0 0 0
20 to <25 6 0.162 0 0 0 0
25 to <30 5 0.135 0 0 0 0
30 to <35 4 0.108 0 0 0 0
35 to <40 2 0.054 0 0 0 0
40 and above 0 0 1 0.167 0 0
Sum 37 1.00 6 1.00 2 1.00

Presence and absence of hydrocephalus and syringomyelia in groups ‘A’, ‘B’ and ‘C’

Type of Arnold–Chiari malformations Presence of hydrocephalus Presence of syringomyelia Absence of hydrocephalus Absence of syringomyelia
Group A 9 19 28 18
Group B 3 1 3 5
Group C 1 2 1 0
Total 13 22 32 23

Length of herniated cerebeller tonsils in type 1 Chiari malformations

Length of herniated cerebeller tonsil in mm Type 1 Chiari malformations
5 to <10 11
10 to <20 21
20 to <30 5
30 and above 0
Total 37

The level of significance of differences of Chiari malformations in different groups

Serial number Comparisons of cases of Chiari malformations between ‘t’ p value
1 Male and Female 0.1273 >0.05
2 Group A and B according to age groups 3.628 <0.01
3 Group A and C according to age groups 4.950 <0.001
4 Group B and C according to age groups 0.7770 >0.05
5 Presence and absence of hydrocephalus 0.7027 >0.05
6 Presence and absence of syringomyelia 0.04203 >0.05
Keywords

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