Chiari Malformation: 15 Cases and Review of the Literature

Chiari malformations represent the main anomalies of nerve structures and result in a low position of the cerebellar tonsils within the upper part of the cervical spinal canal with or without other associated intracranial or extracranial defects such as hydrocephalus, syrinx, encephalocele or spinal dysraphism. Our work is a retrospective study spread over 5 years; from January 2015 to December 2019, involving 15 patients with Chiari I or II malformation, hospitalized within the two neurosurgery departments of the Ibn Rochd University Hospital of Casablanca. A male predominance was observed, with 9 males and 6 females. 12 patients had Chiari I malformation, and 3 patients had Chiari II (age range: 14–48; mean age: 33). Time to diagnosis ranged from 2 to 25 years, with an average of 10 years.

Revealing signs were dominated by motor disorders (73%), sensory disorders (73%) and painful symptoms (53%). Clinical examination of our patients revealed a pyramidal syndrome in 20% of cases, a motor deficit and syringomyelia dissociation in 60% of patients, damage to the cranial pairs and scoliosis were noted in 13% of cases, and 6% of patients had distal amyotrophy. MRI was the examination of choice due to its specificity and sensitivity. It confirmed the diagnosis of Chiari malformation, and syringomyelia was noted in 60% of cases. CT remains advantageous for exploring bone anomalies, which were noted in 26% of cases. All patients underwent craniocervical decompression with dural reconstruction. Shortterm outcomes were generally favorable. Improvement was observed in 73% of cases and stabilization in 13%. No deaths were reported. Surgical treatment is currently the only option, and surgical techniques are constantly evolving to guarantee stable and prolonged improvement and to reduce the risk of morbidity and surgical complications.

Introduction

The cervical-occipital hinge (MCCO) is a complex anatomical and functional unit, a veritable crossroads of anatomical structures and nerve pathways, joining the skull to the spine. It is formed by the occiput (C0), atlas (C1), and axis (C2) [1]. Chiari malformations are the main anomalies of the nerve structures and result in a low position of the cerebellar tonsils within the upper part of the cervical spinal canal, with or without other associated intracranial or extracranial defects such as hydrocephalus, syrinx, encephalocele or spinal dysraphism [2]. MRI has contributed to our understanding of the pathophysiology of Chiari malformation as we know it today [2]. The most common Chiari malformation is type I [2], occurring mainly in adults but also in children, and characterized by elongation of the cerebellar tonsils and the inner part of the inferior lobes of the cerebellum in a conical conformation accompanying the bulb into the spinal canal [3]. Chiari I occurs in 1 in 1000 births. There is a slight female predominance of 3/1 [4]. Chiari II is associated with neural tube defects, particularly myelomeningocele, in around 90% of cases [5].

Therapeutic modalities continue to evolve, and all surgical techniques share the common goal of requiring decompression of the foramen magnum region (see Fig. 1) [6]. Minimally invasive techniques similar to those used in the spine include smaller incisions, less soft tissue damage, less dural manipulation, shorter hospital stays, faster recovery, and fewer complications [6]. With this in mind, we aimed to re-evaluate this pathology and describe its epidemiological, diagnostic, and therapeutic particularities because of their great interest in its day-to-day management.

Fig. 1. Sagittal sections of a cervical-occipital MRI in T2 sequence in a patient with a Chiari I malformation; a. preoperative, b. evolution after 2 years postoperatively, showing the formation of a neo-large cistern and reduction in the volume of the cervical syringomyelia.

Method

Our study was retrospective, conducted over 5 years from January 2015 to December 2019, carried out within the two neurosurgery departments of the Ibn Rochd University Hospital Center in Casablanca. The criteria for including and excluding patients in our study are as follows:

1. Inclusion criteria: We included all patients admitted for surgical cure of clinically diagnosed and radiologically confirmed Chiari malformation. Diagnosis of Chiari malformation is made on cerebral and/or cervical spinal cord MRI.
2. Exclusion criteria: We excluded from our study any patient who did not meet the above criteria.
3. Ethical considerations: The present study was conducted within the framework of scientific and educational research. It was carried out in full compliance with the legal and ethical rules governing the status of patients, which govern scientific work.

Results

The annual frequency of admission of patients with Chiari malformation was 3 per year; in our series, we collected 12 records of patients with Chiari malformation type I (80%) versus 3 records of patients with Chiari malformation type II (20%). The mean age of our patients was 33 years, with extremes ranging from 14 to 48 years (see Table I). The mean age of patients with Chiari type I malformation was 30 years, with extremes ranging from 18 to 47 years. The average age of patients with Chiari type II malformation was 46, with extremes ranging from 45 to 48 years.

Table I. Distribution of Patients by Age

	0–10years	11–20years	21–30years	31–40years	41–50years
Number of cases	0	3	3	4	5
Percentage	0%	20%	20%	26%	33%

The correlation between gender and Chiari malformation type I or II showed a predominance of type I and II in male patients, with a frequency of 58% of cases and a frequency of 66% of cases for type II. The diagnostic delay, i.e., the time elapsed between the appearance of the first clinical sign and the patient’s hospitalization (confirmation of the diagnosis), was 10 years, with extremes ranging from 2 years to 25 years. Painful symptoms such as headache, CKD and paresthesia prompted 50% of patients to seek medical attention. Other signs, isolated or associated with pain, were also indicative of the disease: neurological deficit (10%) and scoliosis (5%). 8 patients expressed painful symptoms, representing a frequency of 53% of cases. These were headache in 5 cases (33%), cervicalgia in 6 cases (40%), dorsalgia in 1 case (6%), cervicobrachial neuralgia in 1 case (6%), lumbago in 1 case (6%) and torticollis in 1 case (6%).

The number of patients with cochleovestibular disorders was 8 (40%); functional impotence secondary to motor deficit was found in 11 patients (73%). Motor deficits were localized to all 4 limbs in 2 cases (13%); one hemicorpus in 2 cases (13%); 2 MI in 1 case (6%); 2 MS in 5 cases (33%); a single limb in 1 case (6%). 11 patients had sensory disorders, representing a frequency of 73%. They took the form of tingling, pins and needles, numbness, paresthesia, hypoesthesia, sensation of burning, vice or electric discharge, and involved the upper limbs in 6 cases (40%); the lower limbs in 3 cases (20%); one hemibody in 2 cases (13%). 6% Visual disorders of the decreased visual acuity type. The neurological examination of our patients revealed Gait disorders in 7 patients and motor disorders of the following types: Tetraparesis in 3 cases, hemiparesis in 3 cases, paraparesis in 1 case, biparesis in 1 case, and monoparesis in 1 case. Pyramidal syndrome was present in 3 patients, Hemi-pyramidal syndrome in 1 case, Tetra-pyramidal syndrome in 2 cases, and Syringomyelic dissociation in 4 cases. Cochleovestibular disorders in 4 cases; Cranial nerve involvement with nystagmus in 2 cases. Amyotrophy distal to the hands was found in 1 patient, mainly involving the thenar and hypothenar muscles (see Table II).

Table II. Physical Examination Findings of Patients in Our Series

Physical signs	Number of cases	%
General examination
Dyspnea	1	6
Cyphoscoliosis	2	13
Clubfoot	1	6
Walking disorder	7	46
Motor deficits
-Tetraparesis	3	20
-Hemiparesis	3	20
-Paraparesis	1	6
-Biparesis	1	6
-Monoparesis	1	–
Pyramidal syndrome
-Hemipyramidal	1	6
-Tetra-pyramidal	2	13
Syringomyelia dissociation (thermo-algesic anesthesia)	9	60

Craniocervical MRI is an essential examination that has supplanted other radiological examinations and was carried out in all our patients (100%). In all cases, it confirmed the diagnosis of Chiari malformation. Craniocervical CT, although less effective for the diagnosis of Chiari malformation, retains its advantages for highlighting bony abnormalities of the CCO or as an alternative in the absence of means. In our series, it was carried out in 5 patients (33%).

Isolated Chiari malformation was found in 6 patients (40%). Syringomyelia was found in 9 patients with syringomyelia alone (60% of cases), 6 patients with Chiari I (40%), and 3 patients with Chiari II (20%). Bone anomalies: 4 patients in our series had bone anomalies (26%). The 4 patients with Chiari I. All patients in our series underwent posterior decompression. Postoperative outcome: Improvement was the rule, with 11 patients (73%) reporting good short-term results. Stabilization of neurological status was the case in 2 patients (13%), and tetraparesis predominantly on the right in one patient.

Discussion

In our series, the annual frequency of admission of our patients was 3 patients per year, whereas Bindal et al. [7] reported 29 cases over 6 years from 1986 to 1991, with an annual frequency of 4.8 patients per year. Similarly, Lakhal [8] reported 54 cases, collated in the neurosurgery department of the University Hospital Center of Fez over 12 years, from 2002 to 2013, with an annual frequency of 4.5 patients per year. In our study, 80% of cases were carriers of Chiari type I and 20% of cases were carriers of Chiari type II. Whereas Henriques Filho and Pratesi [9], in their Brazilian study, reported 36% of Chiari type I malformations and 64% of Chiari type II (see Table III).

Table III. Chiari Malformations in the Literature

Study	Country	Period	Numberof cases	Patient(frequency/year)
Lakhal [8]	Morocco	2002–2013	54	4.5
Bălaşa and Gherasim [15]	Romania	2008–2012	17	3.4
Öktem et al. [16]	Turkey	2013–2015	100	4
Harkani [17]	Morocco	2009–2017	40	4.44
This study	Morocco	2015–2019	15	3

The majority of previous studies have involved young subjects [10]. Chiari I malformation occurs with a slight female predominance (1.3/1). Chiari II occurs without gender predominance [2]. In our work, we noted a male predominance (60%) with a sex ratio of 1.5 (see Table IV) In our series, the mean duration of evolution is 4 years (between 2 and 19 years), whereas it was 8 years (between 6 months and 41 years) in the series reported by Parker [11]. The most common presentation is sub-occipital headache and/or neck pain (80%) [11]. In our study, pain was the main reason for consultation and was noted in 53% of cases.

Table IV. Average Age of Chiari Malformation according to the Literature

Study	Country	Number of cases	Average age (years)	Age range (years)
Dlouhy et al. [10]	Canada	109	17.7	2–61
Aghakhani et al. [18]	France	157	38.3	16–75
Milhorat et al. [19]	USA	364	24.9	–
Henriques Filho and Pratesi [9]	Brazil	75	22.5	2–70
Lakhal [8]	Morocco	71	29.4	3–59
Bindal et al. [7]	USA	29	45	18–66
Harkani [17]	Morocco	40	18.88	1 month–69
This study	Morocco	15	33.46	14–48

Cervical signs: Cervicalgia or cervicobrachial neuralgia were frequent (50% of cases), and inaugural in 20% of cases [12]. There may also be recurrent torticollis and episodes of painful neck blockage associated with chronic tonsillar involvement (6). In our study, cervicalgia was noted in 40% of patients, cervicobrachial neuralgia in 6% and torticollis in 6%. Lin et al. [6] found functional impotence in 13 out of 39 patients (33%). Our work has shown that functional impotence (73%) ranks first in terms of frequency. In the series by Lakdal [8], sensory disorders were reported in 31 patients. They were paresthesias or hypoesthesias. In our series, sensory disorders were present in 11 patients. They took the form of tingling, pins and needles, numbness, paresthesia, hypoesthesia, burning sensation, vice or electric discharge (see Table V).

Table V. Functional Signs of Chiari Malformations Reported in Other Studies and This Study

Symptoms	Milhoratet al. [19]	Nkusiet al. [20]	Thisstudy
Headaches	81%	66.70%	53%
Neck pain	34.3%	61.90%	33%
Respiratory disorders	38.4%	–	6%
Swallowing disorders	43%	5%	–
Motor disorders	57.1%	65%	60%
Sensory disorders	59%	40%	73%
Walking disorders	52%	19.05%	46%
Hearing problems	74%	–	40%
Visual disorders	34.6%	11.10%	6%
Amyotrophy	17%	–	6%
Sphincter disorders	19.7%	5%	26%

In the series by Alzate et al. [13], 12% of patients had a motor deficit (paresis in 6% of cases, paraparesis in 4% of cases, and tetraparesis in 2% of cases). In our study, we report 60% of patients with a motor deficit (tetraparesis in 20% of cases, hemiparesis in 20% of cases, paraparesis in 6% of cases, biparesis in 6% of cases, and monoparesis in 6% of cases).

Sensory disorders mainly affect thermo-algesic sensitivity, resulting in syringomyelic dissociation syndrome, which is characterized by dissociated and suspended sensory involvement, with hypo or thermal anesthesia to cold and/or heat, and painful anesthesia due to damage to spinothalamic fascicles. The longer the course, the clearer and more clinically complete the syndrome. Epicritic and deep sensibility are rarely affected [13].

Conservative medical treatment, combining cervical immobilization with a cervical collar and anti-inflammatory and analgesic treatment, does not achieve lasting improvement in cases of neurological suffering, but it does limit the worsening of nerve damage in certain anomalies: atloido-axoid dislocation, for example, has a preventive role, as an alternative to waiting for surgical treatment [14]. Surgical treatment is the only effective treatment for symptomatic Chiari malformations. It offers appreciable clinical improvement in the neurological complications of Chiari malformations. The indication for surgical treatment depends above all on the degree of neurological suffering and the progression of symptoms and has been associated with a wide spectrum of intraoperative and postoperative complications [14]. Postoperatively, patients’ condition has been reassessed at follow-up, with patients reviewed at 1, 3, 6, and 12 months, and annually thereafter [15]. MRI follow-up is performed between 6 and 12 months postoperatively and will be repeated at 12–24 months if the size of the syringomyelitic cavities has not sufficiently decreased in the previous image [15], [16]. The complication rate averages 21% [15] (see Table VI).

Table VI. Overall Therapeutic Results of Posterior DOD in Selected Studies

Selected study	Improvement	Stabilization	Worsening (Aggravation of syringomyelia on MRI)
van Houweninge Graftdijk [21]	81%	19%	0%
Klekamp [22]	73.6%	21%	5.5%
Our study	80%	13%	6%

Conclusion

The definition of Chiari malformation has evolved with the evolution of neurological diagnostic capabilities and knowledge of pathophysiology. MRI remains the key examination for diagnosis, and decompression of the posterior cerebral fossa with dural plasty is the technique adopted by our department. The results are satisfactory, both clinically and radiologically, and in terms of syringomyelia, with a low complication rate.