Subjects in a darkroom saw an array of five phosphorescent objects on a circular table and, after a short delay, indicated which object had been moved. During the delay the subject, the table or a phosphorescent landmark external to the array was moved (a rotation about the centre of the table) either alone or together. The subject then had to indicate which one of the five objects had been moved. A fully factorial design was used to detect the use of three types of representations of object location: (i) visual snapshots; (ii) egocentric representations updated by self-motion; and (iii) representations relative to the external cue. Improved performance was seen whenever the test array was oriented consistently with any of these stored representations. The influence of representations (i) and (ii) replicates previous work. The influence of representation (iii) is a novel finding which implies that allocentric representations play a role in spatial memory, even over short distances and times. The effect of the external cue was greater when initially experienced as stable. Females out-performed males except when the array was consistent with self-motion but not visual snapshots. These results enable a simple egocentric model of spatial memory to be extended to address largescale navigation, including the effects of allocentric knowledge, landmark stability and gender. q

Mitochondrial disorders are a clinically heterogeneous group of disorders that are caused by defects in the respiratory chain, the metabolic pathway of the adenosine tri-phosphate (ATP) production system. Epilepsy is a common and important feature of these disorders and its management can be challenging. Epileptic seizures in the context of mitochondrial disease are usually treated with conventional anti-epileptic medication, apart from valproic acid. However, in accordance with the treatment of intractable epilepsy where there are limited treatment options, the ketogenic diet (KD) has been considered as an alternative therapy. The use of the KD and its more palatable formulations has shown promising results. It is especially indicated and effective in the treatment of mitochondrial disorders due to complex I deficiency. Further research into the mechanism of action and the neuroprotective properties of the KD will allow more targeted therapeutic strategies and thus optimize the treatment of both epilepsy in the context of mitochondrial disorders but also in other neurodegenerative disorders.

This is a case of a newborn male who was diagnosed in the first month of life with tuberous sclerosis following an incidental ultrasound finding of unilateral ventriculomegaly at 36+6 weeks gestation. The antenatal ultrasound scan at 36+6 weeks was performed to establish fetal lie. Subsequent fetal brain MRI showed lesions that were initially thought to be haemorrhages, but turned out to be features of tuberous sclerosis. The baby also had five cardiac rhabdomyomas and multiple ash leaf macules. This was an unusual presentation of tuberous sclerosis, which on average is diagnosed later (mean age of diagnosis is 5 years). It also illustrates two important points: that subependymal nodules and haemorrhage can have a similar radiological appearance on antenatal MRI and cranial ultrasound and that routine antenatal ultrasound screening will miss the majority of cardiac rhabdomyomas.

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