Case history: a 5-month-old boy was referred to clinic because his head circumference had jumped from below the 25th to the 75th centile and his GP felt that he had a prominent anterior fontanelle. He was developmentally normal with some noticeable frontal bossing. There had been concerns about his mother having had “hydrocephalus” when she was a baby.
Benign enlargement of the subarachnoid space in infancy (BESS)
- usually involves the frontal lobe subarachnoid spaces
- characterised clinically by a widened fontanelle, macrocephaly and/or frontal bossing
- M > F
- often a family history
- majority are neurodevelopmentally normal
- head circumference climbs through the centiles, plateauing on one of the top 2 centiles in late infancy
- unclear pathophysiology
- a transient accumulation of cerebrospinal fluid in the frontal region or delayed development or function of the arachnoid villi at the sagittal sinus?
- cranial ultrasound / MRI show extra fluid around the brain frontally but no ventricular enlargement
- There’s a more scientific and detailed radiological description at https://radiopaedia.org/articles/benign-enlargement-of-the-subarachnoid-space-in-infancy
- can be complicated by chronic subdural haemorrhage possibly secondary to the stretching of subdural veins (Papasian, 2000)
- type 1 glutaric aciduria also presents with increasing head size but these children are not developmentally normal and have other signs on their cranial imaging (Biswas, 2016)
- more information at J Pediatr Neurosci. 2014 May-Aug; 9(2): 129–131 although I’m not convinced of the need for the follow up imaging advocated here, especially if it requires a general anaesthetic
- The literature suggests that BESS resolves spontaneously by 2 years.
- The macrocephaly is likely to persist
The head circumference of the baby presented above plateaued between the top 2 centiles at 10 months. He remains neurodevelopmentally normal.
Picture courtesy of Dr Abdel-Rahman Abdel-Halim, from the case https://radiopaedia.org/cases/29