By age 2, children are developing foundational language processing skills, such as quickly recognizing words and predicting words before they occur. How do these skills relate to children's structural knowledge of vocabulary? Multiple aspects of language processing were simultaneously measured in a sample of 2-to-5year-olds (N = 215): While older children were more fluent at recognizing words, at predicting words in a graded fashion, and at revising incorrect predictions, only revision was associated with concurrent vocabulary knowledge once age was accounted for. However, an exploratory longitudinal follow-up (N = 55) then found that word recognition and prediction skills were associated with rate of subsequent vocabulary development, but revision skills were not. We argue that prediction skills may facilitate language learning through enhancing processing speed.

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Increasing use of nitrous oxide as a recreational drug has been reported among young adults in western countries over the past decade. We present two cases of young males presenting to the Emergency Department (ED) of a large urban university hospital in Dublin with progressive neurological dysfunction related to nitrous oxide use. We review the pathophysiology, clinical features and treatment of nitrous oxide neurotoxicity. It is important that clinicians are aware of this evolving public health issue and are able to recognize the clinical features of this rare presentation, which may become more common in Irish EDs and GP surgeries as nitrous oxide abuse becomes more prevalent.

An 8-year-old boy presented with acute urinary retention 1 week after the onset of a classical primary varicella (chickenpox) rash. Examination confirmed a bladder palpable at the umbilicus. The prepuce was oedematous with a large vesicle on the glans penis obscuring the urethral meatus (Fig. 1).Under general anaesthesia the vesicle was incised and drained. Passage of a urethral catheter was precluded by meatal induration; a 16F suprapubic catheter was therefore inserted (Fig. 2). Following removal of the suprapubic catheter the urethral urinary stream was Fig. 2 Suprapubic catheter in situ. Chickenpox vesicle can be seen on the abdominal wall.unsatisfactory but was restored following dilatation of a meatal stricture. A rising antibody titre confirmed varicella-zoster infection. CommentPrimary exposure to the varicella-zoster virus usually produces systemic disturbance accompanied by widespread crops of vesicles (chickenpox). Herpes zoster (shingles) represents a reactivation of the virus in the dorsal root ganglion, producing the typical vesicular eruption in the corresponding sensory dermatome. Involvement of the sacral plexus resulting in urinary retention is well documented in shingles (Davidsohn, 1890; Rankin and Sutton, 1969;Richmond, 1974). However, we report acute urinary retention as a complication of chickenpox, an association which has not been reported previously.The precise cause of the acute urinary retention in our patient is unclear. However, it is possible that the following factors were involved: the neurogenic effect of primary varicella infection on the sacral plexus; the mechanical effect of the vesicle and associated induration occluding the Fig. 1 Vesicle on glans penis with local oedema and induration.546 CASE REPORTS 547 external urethral meatus; the discomfort experienced when attempting micturition. Acknowledgement

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