Psychological Medicine

Original Articles

Brain morphometry volume in autistic spectrum disorder: a magnetic resonance imaging study of adults

B. Hallahana1a2 c1, E. M. Dalya2, G. McAlonana1, E. Lotha1, F. Toala2, F. O'Briena2, D. Robertsona1, S. Halesa1, C. Murphya1, K. C. Murphya2 and D. G. M. Murphya1

a1 Section of Brain Maturation, Department of Psychological Medicine, Institute of Psychiatry, King's College, London, UK

a2 Department of Psychiatry, Royal College of Surgeons in Ireland, Beaumont Hospital, Dublin, Republic of Ireland


Background Several prior reports have found that some young children with autism spectrum disorder [ASD; including autism and Asperger's syndrome and pervasive developmental disorder – not otherwise specified (PDD-NOS)] have a significant increase in head size and brain weight. However, the findings from older children and adults with ASD are inconsistent. This may reflect the relatively small sample sizes that were studied, clinical heterogeneity, or age-related brain differences.

Method Hence, we measured head size (intracranial volume), and the bulk volume of ventricular and peripheral cerebrospinal fluid (CSF), lobar brain, and cerebellum in 114 people with ASD and 60 controls aged between 18 and 58 years. The ASD sample included 80 people with Asperger's syndrome, 28 with autism and six with PDD-NOS.

Results There was no significant between-group difference in head and/or lobar brain matter volume. However, compared with controls, each ASD subgroup had a significantly smaller cerebellar volume, and a significantly larger volume of peripheral CSF.

Conclusions Within ASD adults, the bulk volume of cerebellum is reduced irrespective of diagnostic subcategory. Also the significant increase in peripheral CSF may reflect differences in cortical maturation and/or ageing.

(Received September 03 2007)

(Revised February 15 2008)

(Accepted March 06 2008)


c1 Address for correspondence: Dr B. Hallahan, Department of Psychiatry, Clinical Science Institute, National University of Ireland Galway, Shantalla, Galway, Republic of Ireland. (Email:


This paper was presented at the International Meeting for Autism Research (IMFAR) in Montreal, Canada, 1–3 June 2006.