A case of a 14-year-old girl suffering from intense headaches is presented. At the first pediatrician's examination, patient had regular findings. Prolonged P100 wave latencies were found by testing visual evoked potentials. After further examination following repeated headaches, Arnold Chiari type I malformation was diagnosed. classified as downward displacement one or both cerebellar tonsils ...

The desert lizards (Meroles: Lacertidae) form a small clade of ground-dwelling taxa inhabiting arid southwest Africa (Arnold, 1991). All seven species have some portion of their range in the Namib Desert, and four of the seven are Namib endemics. Their close geographic ties to the Namib are hypothesized to reflect an interesting pattern of speciation, one in which the lineage infiltrated progre...

EPIDEMIOLOGY Cervical artery dissection accounts for up to 20% of strokes in patients under 30 years of age (Bogousslavsky et al. 1987). The incidence of carotid dissection is about 2–3 per 100 000 per year (Schievink et al. 1993; Giroud et al. 1995); the incidence of cervical dissection must be higher because these fi gures do not take into account vertebral dissection (about 25% of all dissec...

In 1986, Niwi nski 13] showed that the alternation hierarchy of the-calculus on binary trees without intersection was strict. But the xed-point terms he considered for proving this result are all equivalent to coB uchi terms (i.e. in 2) with intersection. Since then, the question of the strictness of the hierarchy of the-calculus on binary trees with intersection was open 4, 14]. Recently, and ...