Position-dependent arm dyskinesia due to severe craniocervical malformation

Abstract

Context

Spinal-generated movement disorders are a complex group of medical conditions, frequently misdiagnosed, originating in the spinal cord or from combined peripheral and central nervous system involvement. In this case report, we describe a novel form of position-dependent dyskinesia due to severe craniocervical malformation.

Findings

An 83-year-old woman with basilar invagination at the C2 vertebra above the line of Chamberlain, occipitocervical lordosis, platybasia with a short clivus, ankylosis of the C1–C2 complex and fusion of the C1 arch developed an unusual pattern of position-dependent left arm dyskinesia triggered by bending her neck forward with simultaneous contact of the flexed elbow with a flat surface. Symptoms did not improve with anticonvulsants and she progressed and died suddenly.

Conclusion/Clinical relevance

A newly described form of position-dependent arm dyskinesia can be associated with severe craniocervical malformation.

Introduction

Spinal-generated movement disorders are a complex group of medical conditions. Frequently misdiagnosed, they originate within the spinal cord or from combined peripheral and central nervous system involvement.¹ The best known examples are segmental and propriospinal myoclonus.¹ Other forms include tonic spasms and secondary paroxysmal dyskinesia-like movements in patients with multiple sclerosis (MS) or neuromyelitis optica and infectious causes, e.g. varicella zoster.^2,3 Severe craniocervical disease can alter brainstem function, e.g. via medullary compression, rarely causing presentations such as “trombone tongue”.⁴ Here, we describe a novel form of position-dependent dyskinesia due to severe craniocervical malformation.

Case

An 83-year-old woman with a history of diabetes and hypertension was referred for a possible stroke, after developing inability to walk and uncontrolled left arm movements over a few weeks. Onset of arm symptoms was abrupt, while bending her neck forward. Despite repeated questioning, details about other symptoms, especially regarding gait disturbance, could not be elicited, because she was more concerned with her postherpetic neuralgia involving her right arm. The neurological exam revealed mild left hemiparesis with dysmetria and position-dependent left arm dyskinesias which were initially interpreted as ballism resulting from a subthalamic stroke; see the video in the supplemental data obtained after obtaining written consent. Head CT showed severe leukoaraiosis, right thalamic and left basal ganglia lacunar strokes and mild cortical atrophy. Risperidone 1 mg QD and clopidogrel 75 mg QD were prescribed, together with gabapentin 300 mg BID for postherpetic neuralgia. A month later, she had not started risperidone. Over the next 10 weeks and 3 office visits her neurological exam and movements remained unchanged despite trials of gabapentin and oxcarbazepine (see video). Brain MRI (Fig. 1) showed no evidence of acute stroke but together with cervical spine CT revealed severe craniocervical malformation, basilar invagination with the C2 vertebra above the line of Chamberlain, occipitocervical lordosis with a basal angle of approximately 150°, platybasia with a short clivus, ankylosis of the C1 and C2 complex and fusion of the C1 arch. Considering her age and co-morbidities, conservative management was recommended. A few months later she was hospitalized and treated for pneumonia but died suddenly after discharge. No autopsy study was conducted.

Figure 1.

Part A: Sagittal views of T1 sequences of Brain MRI revealing severe craniocervical malformation with C2 vertebra at the level of the Chamberlain line and significant brainstem traction. Part B: Axial views of T2 sequences of Brain MRI, reinforcing the presence of small vessel disease and brain atrophy, as well as craniocervical malformation. DWI sequence did not disclose evidence for acute or subacute ischemic stroke. Part C: Sagittal views of Cervical Spine CT scan reveals severe craniocervical malformation severe, basilar invagination with C2 above the Chamberlain line, occipitocervical lordosis with basal angle around 150°, platybasia with a short clivus, ankylosis of C1 and C2 complex, fusion of C1 arch.

Conclusion/Clinical relevance

Karl von Rokitansky was the first to report platybasia and Ernst Alexander Homén the first to relate severe neurological manifestations to an odontoid process compressing the medulla oblongata.⁵ To our knowledge, our patient’s movement disorder associated with craniocervical malformation has not been previously reported. She experienced left arm dyskinesia when she bent her neck and flexed the forearm while touching the elbow on a flat surface.

Myoclonus is a movement disorder characterized by brief, abrupt and involuntary contractions of a single muscle or groups of muscles.⁶ Spinal myoclonus can be divided into segmental and propriospinal myoclonus.⁷ Some phenomenological aspects observed in our patient resemble propriospinal spinal myoclonus (patient 6 in the series of Termsarasab et al.).¹ Symptoms only occurred with neck flexion at specific angles, making a psychogenic causation unlikely and reinforcing the importance of brainstem and/or spinal cord traction, possibly with ephaptic activation of motor pathways.⁸ Similar malformations may lead to episodes of tetraparesis and/or apnea.⁹ The left arm dyskinetic episodes continued until her death, which may have resulted from sudden and more severe brainstem compression. Our findings also resemble paroxysmal dyskinesia- or dystonia-like movements in patients with MS “precipitated by sudden or voluntary movements and by mere intention to move”.³ While we did not rule out a varicella-induced disorder, the clinical course is not consistent with this condition.² Other causes of spinal-generated myoclonus/movement are autoimmune (usually paraneoplastic)¹⁰ and tumors.¹¹ In our patient there was no evidence for either of these conditions and craniocervical malformation was an obvious cause.

Milder forms of CNS position-dependent arm levitation in the setting of parietal stroke, progressive supranuclear palsy and corticobasal degeneration were previously reported by one of the authors and others.^12–14 However, these cases differ in magnitude from what we report here and do not mimic ballism, as seen in our patient. In addition to the similarity to propriospinal spinal myoclonus, the spinal cord as the origin of the movement disorder is favored over brainstem/medulla compression since brainstem movement disorders tend to be more automatic and repetitive as for instance in the report of trombone tongue.⁴ In that case, the patient exhibited repeated tongue protrusion at 2–3 movements/second, resembling a trombone hand slide. The movement vanished after surgical correction of the craniocervical malformation. Another reason to conclude that the movement disorder was generated at the spinal cord and not at the brainstem level is the lack of respiratory and facial involvement, as indeed no cranial nerve involvement was observed.

Lastly, a wide range of medications has been used to treat spinal myoclonus. In most instances medical therapies including benzodiazepines, anticonvulsants and baclofen are disappointing, especially when there is clear spinal cord compression. Surgical treatments have also been advocated.^1,3,6–8 In our patient, gabapentin was briefly tried without significant improvement and additional therapy could not be tried since she died.

In summary, craniocervical malformation can lead to severe position-dependent arm dyskinesia. Without neurosurgical exploration or advanced neurophysiological studies, we can only speculate about the possibility of ephaptic activation of descending motor pathways and cannot pinpoint the anatomical pathways underlying the described phenomenology, although spinal cord and not brainstem involvement is favored.

Disclaimer statements

Contributors: None

Funding: None

Conflict of interest: The authors certify that they have no financial or other conflict of interest pertinent to the subject of this paper.