Paroxysmal and non-paroxysmal dystonia in 3 patients with biallelic ECHS1 variants: Expanding the neurological spectrum and therapeutic approaches.

BACKGROUND: ECHS1 encodes the mitochondrial short chain enoyl CoA hydratase 1 (SCEH). Biallelic ECHS1 variants have been associated with Leigh-like presentations and milder phenotypes with paroxysmal exercise-induced dystonia. PATIENTS/METHODS: We used exome sequencing to investigate molecular bases of paroxysmal and non-paroxysmal dystonia in three patients and performed functional studies in fibroblasts. Disease presentation and response upon dietary interventions were documented. RESULTS: We identified compound heterozygous ECHS1 missense variants in all individuals; all of them harbouring an c.518C > T (p.Ala173Val) variant. SCEH activity was impaired in patients' fibroblasts, respiratory chain-, and pyruvate-dehydrogenase-complex activities were normal in one individual. Patient 1 presented from the age of 2.5 years on with paroxysmal opisthotonic posturing. Patient 2 had a first metabolic crisis at the age 20 months developing recurrent exercise-induced dystonic episodes. Disease history of patient 3 was unremarkable for neurological findings until he first presented at the age of 20 years with persistent dystonia. Ketogenic diet had beneficial effects in patient 1. Neither ketogenic nor low protein diets led to milder symptoms in patient 2. Patient 3 benefits from low protein diet with improvement of his torticollis. CONCLUSIONS: In line with literature, our findings corroborate that the pathogenic ECHS1 variant c.518C > T (p.Ala173Val) is associated with milder phenotypes characterized by paroxysmal and non-paroxysmal dystonia. Because of the potentially treatable defect, especially in milder affected patients, it is important to consider SCEH deficiency not only in patients with Leigh-like syndrome but also in patients with paroxysmal dystonia and normal neurological findings between episodes.

Paroxysmal head drops with ataxia-like symptoms presenting as Sandifer syndrome in a 3-year old girl.

We present a case of Sandifer syndrome in a 3-year-old girl who initially presented with a history of recurrent paroxysmal head drops associated with ataxia-like symptoms and recurrent falls sustaining a clavicular fracture on one occasion. She was referred to and seen by the paediatric neurologist. Physical examination, electroencephalogram, MRI brain, electromyograph single fibre study and blood tests were all normal. With the history of hiccups and choking-like episodes she was referred to the speech and language therapist (SALT). SALT assessment did not reveal indications of swallowing impairment or possible aspiration. A barium swallow later showed small amount of reflux into the distal oesophagus. This prompted a trial of lansoprazole and she was referral to the gastroenterologists. Endoscopy and oesophageal manometry were essentially normal. However, the pH impedance study revealed severe gastro-oesophageal reflux disease. She continued with lansoprazole and dairy-free diet and her symptoms resolved.

Inhibitory Basal Ganglia Inputs Induce Excitatory Motor Signals in the Thalamus.

Basal ganglia (BG) circuits orchestrate complex motor behaviors predominantly via inhibitory synaptic outputs. Although these inhibitory BG outputs are known to reduce the excitability of postsynaptic target neurons, precisely how this change impairs motor performance remains poorly understood. Here, we show that optogenetic photostimulation of inhibitory BG inputs from the globus pallidus induces a surge of action potentials in the ventrolateral thalamic (VL) neurons and muscle contractions during the post-inhibitory period. Reduction of the neuronal population with this post-inhibitory rebound firing by knockout of T-type Ca2+ channels or photoinhibition abolishes multiple motor responses induced by the inhibitory BG input. In a low dopamine state, the number of VL neurons showing post-inhibitory firing increases, while reducing the number of active VL neurons via photoinhibition of BG input, effectively prevents Parkinson disease (PD)-like motor symptoms. Thus, BG inhibitory input generates excitatory motor signals in the thalamus and, in excess, promotes PD-like motor abnormalities. VIDEO ABSTRACT.

Pyruvate dehydrogenase E2 deficiency: a potentially treatable cause of episodic dystonia.

The association of progressive episodic dystonia and learning disability with distinctive neuroimaging findings may lead to consideration of atypical Pantothenate Kinase Associated Neurodegeneration (PKAN) and investigations directed towards that diagnosis. Recent reports indicate that deficiency of dihydrolipoamide acetyltransferase, the E2 component of the pyruvate dehydrogenase complex, may present similarly, and that this disorder should also be considered in the differential diagnosis. We describe two sisters with early onset episodic dystonia and pyruvate dehydrogenase deficiency caused by defects in the E2 subunit. Both have neuroimaging features similar to previously described patients and have mutations in the DLAT gene. As this condition is potentially treatable with a ketogenic diet, the possibility of this diagnosis should be considered in similar cases.

Paroxysmal nonkinesigenic dystonia and celiac disease.

Celiac disease has been associated with ataxia and other neurological signs but has not been associated with paroxysmal nonkinesigenic dyskinesias (PNKD) to date. We present a child with biopsy-proven celiac disease and a movement disorder resembling PNKD since the age of 6 months. She had complete resolution of her neurological symptoms with introduction of a gluten-free diet. Because a susceptibility locus for celiac disease has been reported on 2q33 and studies in PNKD show linkage to 2q, this report suggests further genetic investigations around this locus may be useful. We also review the literature regarding the genetic susceptibility to PNKD and celiac disease.