Dystonia, myoclonus, and encephalopathy in a single patient: A rare association of moyamoya.

Moyamoya disease (MMD) is a rare neurovascular disorder which pathologically, is a chronic cerebrovasculopathy. It is characterized by stenosis of the internal carotid artery (ICA) and the main branches within the circle of Willis with consecutive development of collateral vessels. There are a few cases in the literature which have described movement disorders as a manifestation of MMD; however these have been uncommonly reported in cases of moyamoya syndrome (MMS). We present a 10-year-old boy with dystonia, myoclonus and encephalopathy like features. These features in association with moyamoya, are rarely described.

Introduction

Moyamoya disease (MMD) is a rare neurovascular disorder which pathologically, is a chronic cerebrovasculopathy. It is characterized by bilateral stenosis or occlusion of the internal carotid artery (ICA) and the main branches within the circle of Willis with prominent arterial collateral circulation. Originally described in the Japanese population, this disease is increasingly being diagnosed throughout the world and represents an important cause of childhood stroke in western countries. The typical neuroradiological findings in MMD can coexist with some well identified medical conditions and in that case, this association is categorized a moyamoya syndrome (MMS).[1] MMD or MMS frequently manifests as transient ischemic attack or seizure in children, but hemorrhagic stroke is also common especially in adults. There are quite a few case reports in the literature which have described movement disorders as a manifestation of MMD; however these have been rarely reported in cases of MMS.[23]

Case Report

A 10-year-old boy belonging to Indo-Aryan ethnicity, and a product of nonconsanguineous marriage with normal birth and developmental history was referred to our outpatient department with history of insidious onset and slowly progressive symptoms in form of shock like jerky movements of right hand for last 4 months which occurred at a frequency of 2–3 episodes/min. The movements used to disappear during sleep and were not associated with any specific aggravating or relieving factors. Concurrently, the child also had a history of the abnormal posturing of right hand while writing his lessons, which used to alter his handwriting. However, he did not complain of any weakness, loss of dexterity or any sensory phenomenon. No family member was affected with a similar illness. Besides, his history was remarkable, for acute onset fever followed by altered sensorium and left focal seizures 4 years back. During the event, he was treated with a provisional diagnosis of viral encephalitis. However, cerebrospinal fluid (CSF) study performed on that occasion did not reveal any abnormality in cytological and biochemical analysis. Viral serology panel including herpes simplex virus (HSV) polymerase chain reaction (PCR) in serum and CSF was negative. PCR for tuberculosis in CSF was also negative. There was no record available for the neuroimaging study done during that event. However, electroencephalogram record was suggestive of generalized slowing, thus pointing toward an encephalitic process. He was treated on lines of viral encephalitis and subsequently discharged on phenytoin with minimal left hemiparesis which did not interfere with his daily activities. On examination, we observed the child while writing, and noticed intermittent dystonic supination of his right wrist resulting in abnormal grasp on pencil and disturbed handwriting. Furthermore, he had intermittent myoclonic jerks of right upper limb, mainly involving distal muscles. Also, noteworthy was the increased tone in extremities, right sided limbs being more rigid as compared to left. Superficial and deep tendon reflexes were, however, normal. The patient had minimal weakness in the left upper and lower limbs, muscle strength being grade 4/5. Rest of the general and systemic examination including slit-lamp evaluation for Kayser-Fleischer ring was unremarkable. Routine and specific blood investigations including complete blood count and peripheral smear examination, serum ceruloplasmin, serum calcium, phosphate, thyroid, and parathyroid hormone assays were normal. Antinuclear antibody, antiphospholipid antibody, antineutrophil cytoplasmic antibody, and human immunodeficiency virus serology were also negative. Magnetic resonance imaging (MRI) of the brain was done which was suggestive of the right frontal predominant cortical and subcortical atrophy along with the absence of bilateral middle cerebral artery flow voids and the presence of multiple abnormal flow voids in different parts of the brain [Figure 1]. MRI angiography of brain revealed total occlusion of bilateral supraclinoid ICA, along with extensive collateralization of vessels resulting in a classical “puff of smoke” appearance, diagnostic of moyamoya phenomenon [Figure 2]. Patient's parents were counseled regarding surgical procedures and the subsequent outcome, but they did not give consent for the same.

Figure 1

(a-c) Right frontal predominant cortical and subcortical atrophy along with (d) absence of bilateral middle cerebral artery flow void and multiple abnormal flow voids in different parts of brain

Figure 2

(a and b) Occlusion of total occlusion of bilateral supraclinoid internal carotid artery along with “puff of smoke” appearance

Discussion

The term “MMS” is used when angiographic moyamoya phenomenon is associated with other medical conditions. These associated conditions may include tuberculosis, Down syndrome, sickle cell anemia, neurofibromatosis 1, glycogen storage disease Type 1, Sjogren syndrome, systemic lupus erythematosus (SLE), recurrent thromboembolic events, radiation, human immunodeficiency syndrome, central nervous system bacterial or viral infection, hereditary spherocytosis, hemophilia, Fanconi's anemia, use of oral contraceptives, head and neck infections, and primary antiphospholipid syndrome to name the important ones.[14]

Our patient did not have any history of cranial irradiation. There was no evidence on physical examination or brain imaging to suggest the diagnosis of Down syndrome, neurofibromatosis Type 1 or glycogen storage disease Type 1.

Disorders such as hemophilia and recurrent thromboembolic events were ruled out by a thorough history and clinical examination. Fanconi's anemia, hereditary spherocytosis and sickle cell anemia were ruled out by a normal complete blood count including peripheral smear examination. Antinuclear antibody, antiphospholipid antibody, and anti-neutrophil cytoplasmic antibody were negative in serum ruling out connective tissue disorders such as SLE, antiphospholipid syndrome, and Sjogren syndrome. Human immunodeficiency virus serology was negative as was PCR of tuberculosis performed in CSF to exclude the possibility of tuberculous meningitis.

Sharfstein et al.[5] reported MMS in patients with acquired immunodeficiency syndrome and postulated virally induced vasculitis as the pathological process involved in its genesis. Fukushima et al. have postulated that HSV encephalitis may have a causal relationship with vasculitis.[6] They reported a case of herpetic meningoencephalitis associated with massive intracerebral hemorrhage, with vasculitic phenomenon having a causal implication for hemorrhage. HSV encephalitis resulting into atherothrombosis and presenting as stroke has also been reported in the literature.[7] It is worth recapitulating here that the patient had a provisional diagnosis of viral encephalitis for his past event and he was treated on lines of HSV encephalitis. Notwithstanding the fact, that his CSF HSV PCR was negative. Although the sensitivity and specificity of CSF PCR for HSV exceeds 95%, false negative cases have been reported and repeat HSV PCR testing with possible serologic testing of the CSF has been recommended in such cases[8] which was not done in the present case. Hence, it is plausible that in our case HSV encephalitis was the primary pathology which possibly caused vasculitis and subsequent development of MMS. On the contraposition, rarely MMD may have an “encephalitis-like” presentation which has been reported in literature.[9] Hence, it is quite possible that this child had rather a MMD, and earlier encephalitis-like presentation was the manifestation of his ongoing illness. Therefore, despite ruling out most of the etiologies for MMS, our diagnosis could not be settled as MMD because HSV encephalitis still remained as a possibility.

Although MMS starts unilaterally by definition but progression to bilateral disease especially in children aged <10 years eventually takes place in 44% of patients on an average between 1.5 and 2.2 years and that is why these children should undergo periodic radiologic follow-up.[101112] Notably, our patient had 4 months history of dystonia and myoclonus, and though the disease was clinically unilateral till date, imaging was suggestive of bilateral occlusion of supraclinoid ICA. Nevertheless, it is possible that the disease process started 4 years back, and it was subclinical initially to manifest only 4 months back.

According to the existing literature, 6% of patients with MMD may develop various movement disorders as an initial manifestation or during their clinical course. These may include chorea, dystonia, and dyskinesia.[23] MMS however, has rarely been reported to have these manifestations. Myoclonus has not been reported as a presenting feature in either of the conditions, although acute myoclonus can present as a manifestation of cortical stroke in these patients. Our patient, though, not precisely classified as MMS or MMD, still presents a rare phenotype of moyamoya phenomenon manifesting with dystonia along with myoclonus. It further paves the way for studies focusing on two important facts: (1) Can MMD present like an encephalopathy? and (2) Can HSV encephalitis result in MMS?

Thus, this case may help in better understanding of the disease in the long run.

Definitive treatment of this condition is revascularization surgery and different surgical procedures both direct and indirect have been described. In direct revascularization, a branch of the external carotid artery (usually the superficial temporal artery) is directly anastomosed to a cortical artery and in indirect techniques, there is placement of vascularized tissue supplied by the external carotid artery (e.g., dura, temporalis muscle, or the superficial temporal artery itself) in direct contact with the brain, leading to an ingrowth of new blood vessels to the underlying cerebral cortex.[1]

Conclusion

MMD or MMS can present with diverse manifestations and hence a thorough workup should be done in all suspected cases. Identification of this disease at an earlier stage, excluding possible associated conditions, and regular follow-up imaging in suspected cases are important aspects of clinical management and help in planning appropriate paradigms for treatment. Definitive treatment in the form of revascularization surgery should be offered to all individuals as early as possible to avoid further complications associated with this disease.

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Conflicts of interest

There are no conflicts of interest.