Case Report

The Fate of Syringomyelia Following Surgery for Chiari Type 1 Malformation

John R Ouma*

Division of Neurosurgery, University of the Witwatersrand, Johannesburg, South Africa

Published Date: 02/12/2020

*Corresponding author: John R Ouma, Division of Neurosurgery, University of the Witwatersrand, Johannesburg, 7 York Road, Parktown 2193, Johannesburg, South Africa

DOI: 10.51931/OAJCS.2020.01.000013


Background: Chiari type 1 malformation [C1M] is a well-recognized entity. Frequently discovered in asymptomatic patients, it sometimes comes to attention on account of Valsalva induced headaches, lower cranial nerve disturbances and long tract spinal signs especially where complicated by syringomyelia. Syringomyelia is the most severe complication of this condition and the one most likely to result in adverse sequelae, hence the great interest in its resolution following treatment of C1M, and by extension, which procedure is most likely to achieve this.

Case Description: An 18-year-old girl was diagnosed with C1M associated with hydrocephalus and treated elsewhere by placement of a ventriculoperitoneal shunt a year before coming to our attention with progression of her symptoms, mainly headache and gait disturbances. Clinical examination revealed long tract motor and sensory disturbances in keeping with an extensive syrinx of her cervical spinal cord; this had progressed despite the shunting procedure. She was offered posterior fossa decompression and duroplasty with rapid improvement in both her clinical as well as radiological pictures.

Conclusion: The literature is replete with different surgical techniques for the management of C1M and associated syringomyelia. This case illustrates the point that a given, proven treatment may not achieve the result and alternative techniques may have to be resorted to.

Keywords: Chiari Type 1 Malformation; Syringomyelia


Chiari Type 1[C1M] malformation is a disorder or deformity of varied causes associated with descent of the cerebellar tonsils at least 4mm below the level of the foramen magnum [1-3]. The causes of C1M are primary and secondary. In primary type, the condition arises de novo while in secondary type, it is associated with “push” factors such as hydrocephalus, brain tumours or other causes of raised intracranial pressure, as well as “pull” factors such as tethered spinal cord and lumbar peritoneal shunts [1-3]. There has been, over the past 40 years, significant evolution in the approach to C1M and its management, from it being thought of as a degenerative disease with no surgical remedies, to radiotherapy being considered appropriate, to the current era where a deeper understanding of its possible aetiologies and multiple corrective surgical options exist [4].

C1M can be an incidental finding in asymptomatic individuals while in others, there may be sub-occipital headaches typically worsened by Valsalva type manoeuvres, deficits of lower cranial nerves and long tract spinal cord signs in instances where syringomyelia complicates the condition [1-3,5].

Syringomyelia, also referred to as syrinx, is a condition in which fluid accumulates in the substance of the spinal cord; depending on the degree to which this happens, the individual may be asymptomatic at one end of the spectrum or severely disabled at the other end [5-7]. Syrinx formation is the most serious consequence of C1M and the one most likely to cause long term sequelae and undermine the quality of life of the affected individual. Hence, the fate of syringomyelia in individuals undergoing surgery for C1M is a matter of great interest. There are various techniques described for the treatment of C1M [2,4]. These include bony decompression only of the foramen magnum with possibly a laminectomy of the first and sometimes second cervical vertebra, posterior fossa decompression and duroplasty [PFDD] with/without arachnoid dissection, posterior fossa decompression with splitting of the outer layer of the dura, and PFDD with tonsillar resection [8-10]. In addition, atlanto-axial fusion has been proposed as a treatment for this, although being a more recent development compared with then other established options, long term follow up data are not yet available for this technique [11-14].

Studies have found no difference in outcome of the syrinx with PFDD regardless of whether or not arachnoid dissection was carried out but where only splitting of the outer layer of dura was done, the result was not as good as the former techniques [8]. Regarding the cerebellar tonsils, there was no discernible difference in syrinx outcome whether these were sacrificed or left intact [9]. Some studies have shown that posterior fossa decompression may not improve the clinical or radiological outcome of syringomyelia in 40% to 50% of patients where persistence, progression, or recurrence of syringomyelia occurs [15] and re- decompression or ventricular shunting procedures have high failure rates [16]. Nevertheless, where there is radiographic failure but good symptom control, a conservative approach is recommended [16]. Contrary to these dismal figures, another study found that following PFDD for C1M, syringomyelia improved in 91.3%, worsened in 3.7% and remained unchanged in the rest [10]. These widely divergent outcomes for the same procedure in different hands suggest that the individual techniques applied by different surgeons at their respective centres for what is supposedly the same operation, as well as differences in follow up may play a big role in what is reported. One aspect that must be considered is the question of the presence of hydrocephalus. In 7-10% of cases of C1M, hydrocephalus is present. 

Where this is the case, the treatment of the hydrocephalus by endoscopic third ventriculostomy has been shown to result in relief of hydrocephalus, tonsillar descent and syringomyelia in 90.5%, 78.5% and 76% respectively of cases [17]. Considering the foregoing, it would appear prudent to suggest that where hydrocephalus exists in the setting of C1M, this should be addressed first. Where this does not obtain, then posterior fossa decompression with or without tonsillar sacrifice and subarachnoid dissection should be offered. In the event of failure of the syringomyelia to resolve and especially if this is symptomatic, then re-do PFDD, atlanto-axial stabilization, as well as syringo-peritoneal or syringo-subarachnoid shunts may be tried [15,16].

Case Description

An 18-year-old girl presented to our facility with complaints of suboccipital headaches and gait difficulty. She had been seen elsewhere two years previously and diagnosed with C1M associated with hydrocephalus. A ventriculoperitoneal shunt was placed. Despite this intervention, she reported that her symptoms had progressed after an initial period of a couple of months following this procedure where she felt slightly better in terms of headache. Clinically she had no deficit of cranial nerve function and her fundi were normal. On long tract examination, she had grade 4/5 weakness in all limbs with spasticity and hyperreflexia in the lower limbs and a suspended sensory loss over the upper trunk. Figure 1 is a sagittal T1 weighted MRI that shows tonsillar descent in keeping with a diagnosis of C1M as well as marked hydrocephalus despite prior ventriculoperitoneal shunting. The upper part of the syrinx is visible. 

Figure 2 is a sagittal T2 weighted MRI scan demonstrating the extent of the cervico-thoracic syrinx cavity. Both Figures 1 and 2 were similar to the pre-VP shunting appearance.She was offered a PFDD with rapid improvement in her clinical symptoms including her limb strength and walking ability as well as radiological improvement in the syrinx in a follow up magnetic resonance imaging [MRI] scan taken 30 days after the surgery. Figure 3 is a sagittal T2 weighted MRI scan obtained 30 days following the procedure, and the remarkable improvement in the syrinx is evident.

Figure 1: Pre-operative sagittal T1 weighted MRI that shows tonsillar descent in keeping with a diagnosis of C1M as well as marked hydrocephalus despite prior ventriculoperitoneal shunting. The upper part of the syrinx is visible.

Figure 2: Pre-operative sagittal T2 weighted MRI scan demonstrating the extent of the cervico-thoracic syrinx cavity, as well as the tonsillar descent. 

Figure 3: Post-operative Sagittal T2 weighted MRI scan obtained 30 days following the procedure, in which the remarkable improvement in the syrinx is evident.


C1M associated with hydrocephalus and complicated by syringomyelia has been treated with cerebrospinal fluid diversion alone, by either endoscopic third ventriculostomy or ventriculoperitoneal shunting with good reported results in as far as resolution of the clinical features and radiological picture are concerned [17]. This case described is an exception, as she failed to respond to this line of treatment. She did do very well with PFDD procedure, which itself has had widely differing outcomes reported by different groups [10,15]. This case illustrates the fact that a single procedure may not be the solution to every case and further research is indicated to establish the most likely surgical procedure to be of benefit in a given case of C1M, to avoid the need for multiple procedures.


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