Correspondence Address: Dr. Vaibhav Mathur D-176, Nirman Nagar, Kings Road, Ajmer Road, Jaipur, Rajasthan. India
Source of Support: None, Conflict of Interest: None
Syringomyelia is described as a fluid-filled cavity within the spinal cord devoid of an ependymal lining. It is best visualized on magnetic resonance imaging (MRI), with the cavity being low intensity on T1-weighted and high intensity on T2-weighted images. The association of syringomyelia with dystonia has been infrequently reported in the medical literature. We herein describe a case of syringomyelia with Chiari 1 malformation and hydrocephalus having writer’s cramp and pseudoathetosis, which as per our review, is a yet undescribed manifestation in previously published literature. Also, we emphasize on the usefulness of spinal MRI in a case of focal dystonia/writer’s cramp if cause is not apparent after initial evaluation and more so if associated with proprioceptive sensory impairment and pseudoathetosis.
How to cite this article: Khandelwal D, Mathur V, Vyas A, Singh M. Syringomyelia with Chiari 1 malformation presenting as focal hand dystonia. Ann Mov Disord 2020;3:173-7
How to cite this URL: Khandelwal D, Mathur V, Vyas A, Singh M. Syringomyelia with Chiari 1 malformation presenting as focal hand dystonia. Ann Mov Disord [serial online] 2020 [cited 2021 May 7];3:173-7. Available from: https://www.aomd.in/text.asp?2020/3/3/173/300255
In our patient, syringomyelia with associated Chiari 1 malformation and hydrocephalus presented as secondary right focal dystonic writer’s cramps with associated pseudoathetosis of fingers of the same hand. Hence, neuroimaging of the cervicothoracic spine is worthwhile in patients of hyperkinetic movement disorders of unclear etiology, even without physical findings that suggest myelopathy.
Syringomyelia, uncommonly, may manifest with movement disorders, including dystonia, myoclonus, tremor, and athetosis. Dystonia and athetosis are prototypically linked to lesions and disorders involving basal ganglia and its connections. Around 18 cases of dystonia associated with syringomyelia have been published till date, although some cases possibly remain unreported and even undiagnosed as cord imaging is not routinely used to evaluate most dystonic conditions. As most syringomyelia patients do not develop dystonia, the presence of a syrinx may only be pathophysiologically relevant in otherwise predisposed individuals, and may not imply causality. Our case herein will add to the current scant literature on the subject and might trigger further insights into possible pathophysiology of this association.
We report the case of a 30-year-old woman, teacher by occupation, with no comorbid illness, presented with abnormal posturing of right hand while writing, making it difficult for her to grip pen just after minutes of writing for the last 25 days. These complaints were acute in onset and were preceded by headache and neck pain, which had started while the patient was looking up with neck extended and cleaning spider webs on her house ceiling around 1 month back. There was no history of pain, any weakness in holding objects, or sensory complaints. There was no difficulty in performing other routine household tasks, which involved her right hand. There was a prior history of episodic headache and vertigo for last 4 years, which used to subside spontaneously. No history of trauma or fever. On examination, cranial nerves were intact, motor examination showed normal bulk and tone; however, there was the presence of dystonic posturing of right hand in outstretched position in the form of hyperextension of right middle finger at metacarpophalangeal, proximal, and distal interphalangeal joints [Figure 1] along with slow random nonrhythmic writhing movements of fingers in right hand, more in right index, ring, and little fingers while in unsupported position [Video 1, Segment 1]. Opening and closing the eyes had no apparent effect on the pattern and severity of these movements. On attempting writing, there was an observable aggravation of dystonia of hand, and her writing became illegible within minutes [Video 1, Segment 2]. She had to repeatedly use her other hand to hold and grip the pen. Deep tendon reflexes were normal on both sides. Sensory examination was normal for pain, touch, and temperature. However, there was impairment in vibration and proprioception distal to wrists. Cerebellar signs were absent, and gait was normal. Investigations including hematological and biochemical screening, autoimmune profile, measurements of the serum ceruloplasmin, urine copper levels, were all normal. Magnetic resonance imaging (MRI) of brain and cervical spine was done, which revealed hydrocephalus [Figure 2] with dilated lateral, third and fourth ventricles, and Chiari malformation More Details type 1 [Figure 2] with cerebellar tonsillar herniation in the cervical canal. There was a large syrinx extending throughout the cervical and dorsal spinal cord [Figure 2]. The cerebrospinal fluid studies including oligoclonal bands, neuromyelitis optica antibodies, and myelin basic protein were also negative. The patient was referred for neurosurgery.
Syrinxes most commonly manifest because of their local effects on spinal cord sensory and motor pathways, characteristically producing a “dissociated sensory loss” (loss of pain and temperature, with preserved proprioception and vibration) and weakness in affected myotomes (commonly the arms and hands). However, we have poor understanding of the potential pathophysiology of syringomyelia-associated dystonia (SAD).
Pathophysiology of syringomyelia-associated dystonia
Basically, loss of inhibition, either at supraspinal or spinal level, is the pathophysiology of dystonic conditions, causing co-contraction of agonist and antagonist muscles and overflow of muscle activity. At the supraspinal/central level, dystonia is now considered a network disorder, where, under normal circumstances, interconnected brain regions (cortex, basal ganglia, thalamus, and cerebellum) work in integration to select, implement, and monitor coordinated movements. Dysfunction of one or more of these areas, or their communication, can produce dystonia.
However, at the spinal cord level, reciprocal inhibition of the antagonistic muscles mediated through group 1a interneurons is influenced both by group 1a afferents from muscle spindles and by descending central influences., Structural spinal cord abnormalities such as syringomyelia could interrupt both of these processes, causing loss of spinal inhibition by reducing the inhibitory interneuron activity. The cerebellum also, in some patients, could be the driver of dystonia. The cerebellum is the target for numerous sensory afferents (via the spinocerebellar tracts) and is likely to have a role in sensory prediction and sensorimotor integration., Thus, disruption of normal cerebellar sensorimotor processing, either as a result of structural distortion or altered connectivity, could also generate dystonia.
Thus, SAD is an unusual form of secondary dystonia, generated by aberrant influences on the dystonia network, either through alteration of sensory inputs, loss of inhibition, or anomalous cerebellar function. Screening for syringomyelia should be considered in cases of young-onset or clinically atypical dystonia.
Previously described cases of movement disorders of spinal origin
Cases of athetosis and dystonia of spinal origin have been previously described in association with various kinds of lesions involving the posterior columns of the spinal cord, more often at the C1-C4 level such as syringomyelia, tumor, spinal cord infarction, cervical myelopathy, myelitis, vitamin B12 deficiency, cervical disc herniation, epidural, and demyelinating lesions.
Comparing with the previously studied patients of SAD [Table 1], our patient clinically differed in having intact sensory examination except for proprioceptive testing, no motor deficits in limbs, presence of writer’s cramps, pseudoathetosis, and radiologically differed in having both Arnold–Chiari malformation type 1 and hydrocephalus.
Table 1: Previous publications on syringomyelia-associated dystonia
In our patient, syringomyelia with associated Chiari 1 malformation and hydrocephalus presented as right focal dystonic type writer’s cramp with associated pseudoathetosis of fingers of same hand. Writer’s cramp, in our patient, was a task-specific focal dystonia interfering with her motor performance while writing. Malfunctioned specific parietal–premotor pathways are likely to be the culprit. Secondary motor disturbances in tasks other than writing can occur in about half of the patients with simple cramps, resulting in progression to dystonic writer’s cramps and eventually to multifocal dystonias.
The involuntary, slow, writhing movement, in our patient, is termed pseudoathetosis, which is clinically indistinguishable from athetosis, but unlike true athetosis, it is associated with a loss of proprioception. Pseudoathetosis may be caused by lesions located anywhere along the sensory pathways, ranging from peripheral nerve to parietal cortex, including posterior columns and thalamus,,, whereas athetosis primarily is a manifestation of basal ganglia lesions.
Henceforth, we suggest that neuroimaging of the cervicothoracic spine may unmask a spectrum of treatable cord disorders in patients with hyperkinetic movement disorders of unclear etiology.
We would like to thank our institution and department for providing us such a giant platform to work on, our patients, whom we serve and learn, and our families and friends who support us in our endeavors.
Amouzandeh A, Grossbach M, Hermsdörfer J, Altenmüller E Pathophysiology of writer’s cramp: An exploratory study on task-specificity and non-motor symptoms using an extended fine-motor testing battery. J Clin Mov Disord 2017; 4:13.