• Excessive blinking and ataxia in a child with occult neuroblastoma and voltage-gated potassium channel antibodies.

      Allen, Nicholas M; McKeon, Andrew; O'Rourke, Declan J; O'Meara, Anne; King, Mary D; Department of Pediatric Neurology, Children's University Hospital, Dublin 1, Ireland. nicholasallen@physicians.ie (2012-05)
      A previously healthy 9-year-old girl presented with a 10-day history of slowly progressive unsteadiness, slurred speech, and behavior change. On examination there was cerebellar ataxia and dysarthria, excessive blinking, subtle perioral myoclonus, and labile mood. The finding of oligoclonal bands in the cerebrospinal fluid prompted paraneoplastic serological evaluation and search for an occult neural crest tumor. Antineuronal nuclear autoantibody type 1 (anti-Hu) and voltage-gated potassium channel complex antibodies were detected in serum. Metaiodobenzylguanidine scan and computed tomography scan of the abdomen showed a localized abdominal mass in the region of the porta hepatis. A diagnosis of occult neuroblastoma was made. Resection of the stage 1 neuroblastoma and treatment with pulsed corticosteroids resulted in resolution of all symptoms and signs. Excessive blinking has rarely been described with neuroblastoma, and, when it is not an isolated finding, it may be a useful clue to this paraneoplastic syndrome. Although voltage-gated potassium channel complex autoimmunity has not been described previously in the setting of neuroblastoma, it is associated with a spectrum of paraneoplastic neurologic manifestations in adults, including peripheral nerve hyperexcitability disorders.
    • Limbic encephalitis in a boy with N-methyl-D-aspartate receptor antibodies.

      Allen, Nicholas M; Lynch, Bryan; Twomey, Eilish; Department of Paediatric Neurology, Children's University Hospital, Dublin, Ireland. (2012-06)
    • Not all twitching is epileptic! Hand myoclonus in a boy with spinal cord tumor.

      Allen, Nicholas M; Moran, Margaret M; King, Mary D; Department of Pediatric Neurology and Clinical Neurophysiology, Children's University Hospital, Dublin, Ireland. (2013-02)
    • "Stiff neonate" with mitochondrial DNA depletion and secondary neurotransmitter defects.

      Moran, Margaret M; Allen, Nicholas M; Treacy, Eileen P; King, Mary D; Department of Paediatric Neurology and Clinical Neurophysiology, Children's University Hospital, Dublin, Ireland. (2011-12)
      Mitochondrial disorders comprise a heterogenous group. A neonate who presented with episodes of severe truncal hypertonia and apnea progressed to a hypokinetic rigid syndrome characterized by hypokinesia, tremulousness, profound head lag, absent suck and gag reflexes, brisk deep tendon reflexes, ankle and jaw clonus, and evidence of autonomic dysfunction. Analysis of cerebrospinal fluid neurotransmitters from age 7 weeks demonstrated low levels of amine metabolites (homovanillic acid and 5-hydroxyindoleacetic acid), tetrahydrobiopterin, and pyridoxal phosphate. Mitochondrial DNA quantitative studies on muscle homogenate demonstrated a mitochondrial DNA depletion disorder. Respiratory chain enzymology demonstrated decreased complex IV activity. Screening for mitochondrial DNA rearrangement disorders and sequencing relevant mitochondrial genes produced negative results. No clinical or biochemical response to treatment with pyridoxal phosphate, tetrahydrobiopterin, or l-dopa occurred. The clinical course was progressive, and the patient died at age 19 months. Mitochondrial disorders causing secondary neurotransmitter diseases are usually severe, but are rarely reported. This diagnosis should be considered in neonates or infants who present with hypertonia, hypokinesia rigidity, and progressive neurodegeneration.