Objective: To report the clinical outcome of one patient treated with pallidal and thalamic DBS for status dystonicus in the context of Niemann Pick disease (NPC)

Background: NPC is a recessively inherited lysosomal disorder associated with cerebellar ataxia, dystonia, cognitive and psychiatric signs. Previous reports found dystonia in 46% of adult-onset NPC patients. The prevalence of status dystonicus is unknown. One case-report of myoclonic storm with fatal outcome was described in a previous series of NPC patients.

Methods: Clinical and radiologic data of a 38-year-old patient suffering from NPC disease of adolescent onset are described. Diagnosis was confirmed by exome sequencing. He underwent MRI-guided surgery for implanting 4 electrodes in 2 different targets (GPi and thalamic Vim/Vop nucleus) in the context of refractory status dystonicus. 

Results: The patient was admitted to hospital due to severe generalized dystonia. Possible triggering factors for status dystonicus were discontinuation of clonazepam (despite a slowly progressive tapering off protocol) and the introduction of miglustat therapy some months earlier. Discontinuation of miglustat, followed by treatment with  intravenous Clonazepam led to partial improvement. PEG feeding tube was placed due to progressive dysphagia. Three months later, he developed daily episodes of severe dystonia with rhabdomyolysis: despite renewal of intravenous clonazepam and further association of Chlorpromazine and Fentanyl, the absence of response motivated the decision of palliative DBS surgery. Progressive adjustment of stimulation settings and drugs (Clonazepam, Gabapentin, Amitriptyline, Hydroxyzine, Phenobarbital, Clozapine) improved movement disorders. Both pallidal and thalamic stimulation were activated at the moment of discharge from hospital. Oral feeding was possible, except for medical treatment. His clinical situation is stable without severe dystonia since that moment with a follow-up of 15 months.

Conclusions: To our knowledge this is the first report of DBS applied to the treatment of complex dystonia in NPC disease. The most probable triggering factor of status dystonicus was discontinuation of clonazepam. Exacerbation of dystonia has not been reported as adverse effect of miglustat. Further research is needed to test the differential role of pallidal and thalamic DBS and drug therapies in the clinical management of this patient 

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MDS Abstracts - https://www.mdsabstracts.org/abstract/status-dystonicus-treated-by-deep-brain-stimulation-in-niemann-pick-type-c/