Key-words:
Chiari presentation - chiari - clinical symptoms
Background
Chiari malformations are a group of clinicopathological entities with a variety of
clinical presentations, different pathophysiology, and variable outcomes. Cerebellar
ectopia is the term used to describe this condition. The first case was reported in
1883 by Cleland, and later in 1891 detailed description was done by a pathologist
Professor Chiari.[[1]],[[2]]
This syndrome is a developmental malformation of the occipital mesodermal somite that
express as herniation of variable degree of different hindbrain structures, commonly
associated with hydrocephalous and syringomyelia. This syndrome is divided into five
subtypes.
Chiari Type 1 malformation is the caudal descent of cerebellar tonsils through the
foramen magnum up to 3–5 mm.[[3]],[[4]] Chiari Type 2 was described in 1896 and consists of the descent of cerebellar vermis,
fourth ventricle, and lower brain stem and has a strong association with myelomeningocele.
This type is called Arnold Chiari malformation and this is the most common form of
Chiari malformation among its sub-types.[[3]],[[5]] Chiari Type 3 malformation is associated with the presence of occipital encephalocele
with hindbrain structures in it.[[3]] Chiari Type 4 malformation is the cerebellar hypoplasia without the actual herniation
and it is the least common form.[[3]] A relatively new subtype of Chiari malformation was described in the past few years,
it consists of an alteration of Cerebrospinal Fluid (CSF) dynamics at the foramen
magnum level. It also has some tilt of the brain stem including pons and medulla and
it has a low level of obex.[[6]],[[7]] Another rare form of Chiari malformation was described, this subgroup has caudal
cerebellar displacement and cerebellar ectopia without spina bifida. This term was
coined as Chiari 1.5.[[8]]
In Chiari malformation Type 1, there is overcrowding of posterior fossa[[9]] and this is associated with other conditions that are not directly related to the
hypoplasia of the skull base. These conditions include hydrocephalous,[[5]] tethered cord syndrome,[[9]] craniosynostosis,[[10]] intracranial mass,[[11]] and some connective tissue disorders.[[12]] Some causes explain the diversity of clinical presentation of patients with Chiari
malformation.
The clinical presentation of Chiari malformation is usually due to either cerebellar
compression, brain stem compression, syringomyelia, hydrocephalous, or hydromyelia
(impairment of normal CSF circulation). According to some studies, the majority of
symptoms are due to spinal cord syrinx formation.[[13]],[[14]],[[15]] Patients can present with pain, weakness, and/or sensory disturbance involving
the upper limbs. Signs on presentation are hand muscle atrophy and weakness, lower
limb spasticity, sensory dysaesthesia, urinary incontinence, or scoliosis.
Strain-related headaches are typical for disturbances in normal CSF flow. Valsalva-related
activities all are considered as trigger factors for this type of headaches. These
headaches are brief and localized to the occipital region occurs in 80%–100% of the
cases.[[16]] There may be some atypical headaches such as generalized and retro-orbital headaches
and these are longer in duration.[[17]] Patients with Chiari zero may present with these types of symptoms.[[6]] This CSF dynamics can also disturb perilymph flow and this is responsible for symptoms
such as tinnitus, dizziness, and hearing loss.[[14]]
Visual impairments including blurring of vision, diplopia, and nystagmus are common
signs of brain stem compression in Chiari malformation,[[18]] and downbeat nystagmus is characteristic of Craniovertebral junction abnormalities
occurs in 75% of cases.[[19]] This occurs due to impaired function of the brain stem nuclei and traction on cranial
nerves, especially the 4th, 6th, and 3rd cranial nerves. Brain stem descent causes
compression and traction on cerebellar pathways and result in balance difficulties
and usually truncal ataxia in 40% of the cases.[[14]],[[20]] Swallowing difficulties occurs in 6%–45% of cases.[[14]] Autonomic disturbances including drop attacks, bradycardia, dyspnea, syncopal episode,
and palpitations were reported in up to 10% of the cases.[[21]],[[22]],[[23]] Syncope, bradycardia, and respiratory difficulties all occurs due to pressure on
the brain stem as a result of tonsillar descent.[[22]],[[24]],[[25]]
Symptoms due to cerebellar descent are either due to direct pressure on the cerebellum
or traction of cerebellar pathways secondary to brain stem herniation as described
earlier. These symptoms include truncal ataxia, nystagmus, and dizziness. The hoarseness,
swallowing difficulties, and tongue fasciculations are due to involvement and traction
on lower cranial nerves.
The rationale of this study is to observe the different clinical presentations of
the patients with Chiari malformation in our population. As the time of initial presentation
is delayed that might change the sign and symptoms with which the patient initially
presents.
Materials and Methods
This was a cross-sectional observational study with prospectively collected data of
46 patients with Chiari malformation who were presented to the Department of Neurosurgery,
Liaquat National Hospital Karachi Pakistan. Liaquat National Hospital is one of the
few major hospitals in the city providing neurosurgical expertise. It has a catchment
area of two million people also people are been referred to this hospital for neurosurgical
care from other hospitals and clinics.
These patients were included in the study from the outpatient department of our hospital
and were characterized accordingly. The demographic data, clinical presentations,
and radiological findings were retrieved from the data bank of the Neurosurgery Department
and the Health Information and Management Services Department by the resident R5 and
a medical officer. The duration of the study is from 2017 to 2020. The institutional
review board approved the research protocols and analyzed using IBM Corp. Released
2017. IBM SPSS Statistics for Windows, Version 25.0. Armonk, NY: IBM Corp.
Statistical analysis
The patient's data will be compiled and analyzed through the Statistical Package for
IBM Corp. Released 2017. IBM SPSS Statistics for Windows, Version 25.0. Armonk, NY:
IBM Corp. Qualitative variables are presented as frequencies and percentages. Quantitative
variables are presented as mean ± standard deviation. Effect modifiers are controlled
through stratification. A Chi-square test is used for finding an association between
categorical variables. P ≤ 0.05 is considered as statistically significant.
Results
According to our data, a total of 46 patients with Chiari malformation were included
in the study. Thirty one were male and 15 were female. The patients were divided into
five groups according to age as shown in [[Table 1]]. The majority of patients were in the second decade of life followed by those within
10 years.
Table 1: Demography
As shown in [[Figure 1]], the majority of patients presented with motor weakness alone that account of 36%
of the patients, around 23% had both motor and sensory deficit, 17% had an only sensory
deficit, and only 8% of the patients presented with headache alone. [[Table 2]] shows a detailed description of motor weakness and sensory weakness in upper and
lower limbs according to different age groups.
Figure 1: Presenting complaints of Chiari patients
Table 2: Pattern of motor and sensory deficit
Chiari malformation is a syndrome associated with the involvement of other systems
also. The most common associated anomalies are myelomeningocele, diastematomyelia,
and curvature deformity. [[Table 3]] shows patients with different Chiari-associated conditions in a different age groups.
Table 3: Associated conditions with Chiari Malformation
The time of presentation plays an important factor. As the disease progress, the symptoms
become more severe and signs become more typical and this may change the presenting
scenario. In case of Chiari malformation progressive and continuous traction on posterior
fossa structures including cerebellum, brain stem, and cranial nerves causes the symptoms
to progress and cause further pathological changes that generate new symptoms, for
example, if the CSF flow is continuously disturbed it will lead to the formation of
the syrinx and can cause hydrocephalous to develop that further precipitate the condition
and changes the clinical presentation. Data regarding syrinx formation and hydrocephalous
in our study are described in [[Table 4]].
Table 4: Association of hydrocephalous and syrinx formation with Chiari malformation
[[Figure 2]] shows the frequency of different signs elicited on the first encounter with the
patient.
Figure 2: Clinical signs on presentation
Discussion
Conventionally, the major presenting clinical features of Chiari malformation are
debilitating headaches, neck pain, dizziness, and visual disturbances.[[26]] This pattern of presentation is present in both adult as well as pediatric populations.[[27]] Studies suggested that the involvement of different parts of the brain stem, tracts,
nuclei, and cranial nerves will lead to different symptoms, age, and duration of the
symptoms also has a role to play. Furthermore, disturbed CSF dynamics and the presence
or absence of hydrocephalous also contribute to the clinical presentation of the patients.
Disturbed CSF dynamics will also lead to syrinx formation in the spinal cord and it
presents as motor weakness involving muscle atrophy, altered reflexes, and spasticity.
This excessive accumulation of fluid in the central canal of the spinal cord will
cause the same pathology as in central cord syndrome.[[28]]
There are several theories have been developed o explain the development of syringomyelia
and hydromyelia. One theory is Gardner's theory[[29]] it states that there is delayed opening of the fourth ventricle which results in
the transmission of the arterial pulse through a patent obex, producing a water hammer
effect that enlarges the central canal. Another theory is William's theory[[30]] it states that hydro syringomyelia results from the pressure difference between
two cavities, that is cranial and spinal cavities. Herniation of cerebellar tonsils
further augments the pressure difference between the two cavities.
Other clinical presentations are due to compression on different structures of the
brain as discussed earlier. Balance, gait difficulty, and nystagmus occurs as a part
of compression on the cerebellum, while hoarseness, swallowing difficulties, facial
weakness, and hearing weakness results when there is direct pressure or traction on
the lower cranial nerves. Moreover, compression on the brain stem causes respiratory
difficulties and autonomic nervous system disturbances.
As discussed earlier, the most common presenting symptom is the occipital headache
that increases on straining, coughing, or sneezing, and the frequency is around 80%–100%,
but in our study, the data have suggested that the most common presenting symptom
is motor weakness and commonly involving the upper limb followed by sensory weakness
and headache which are present in less number of patients, this explains the factor
of delayed presentation and lack of awareness regarding the disease. The lower limb
involvement is either due to syrinx formation or cerebellum involvement. However,
nystagmus was also present in a significant number of cases.
Most of our patients had hydrocephalous and myelomeningocele and most of them were
children as described previously in results. We have done CSF diversion in around
30% of cases and this will lead to resolution of the symptoms and syrinx.
Owning to delayed presentation in our population mostly patients present with motor
weakness and walking difficulties and delayed presentation can affect the outcome
of treatment.
Conclusion
Clinical presentation in our population differs from other studies. Motor weakness
and sensory deficits are being the most common complaint on initial presentation.
The reason behind this is the delayed presentation of the patient and lack of awareness
of the disease and ultimately it will alter the outcome of disease and treatment.
