{'fraction_non_alphanumeric': 0.019249278152069296, 'fraction_numerical': 0.02021174205967276, 'mean_word_length': 4.842696629213483, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Letter to the editor. Anomalies of the A1 segment.

We would like to comment on the recent publication by Chakraborty et Al, on anomalies of A1 (Chakraborty S, Fanning NF, terBrugge KG: Bilateral infraoptic origin of anterior cerebral arteries: a rare anomaly and its embryological and clinical significance. Interventional Neuroradiology 12:155-159,2006) We wish to point out that we have also reported two new cases in 1989. The first case was exceptional with a bilateral infraoptic course of the anterior cerebral artery and persistence of the normal A1 portion of the right and left anterior cerebral arteries. The second patient had a unilateral infraoptic course of the right anterior cerebral artery which divided at the chiasm level into two per- icallosal arteries; neither right nor left A1 was in the normal location. 
 
On the basis of these two new cases together with other cases collected in a review of the literature, various hypotheses to explain to explain the embryological origin of these A1 anomalies were discussed.