Purpose or Case Report: The presence of a thin midline band or nodule like grey matter structure traversing the hypothalamic region on magnetic resonance imaging (MRI) is a recently reported neuroimaging finding. This has been termed as interhypothalamic adhesion (IHA). To date, no histopathological correlation has been published on the precise nature of IHA and whether it represents a developmental anomaly, cerebral malformation or the sequela of cerebral insult. We aim to look at a cohort of patients with IHA and determine its association with other cerebral anomalies seen in these cases.
Methods & Materials: Cases of IHA seen on brain MRIs at a single tertiary paediatric centre on 1.5T and 3T performed from September 2001 and September 2019 were compiled from a search of MRI reports on the local radiology information system. Cases were subsequently evaluated on available T1 and T2 weighted sequences in multiple planes on the local PACS viewer (Fuji Synapse) by two fellowship trained consultant paediatric radiologists. Basic demographic and clinical information was recorded for each patient. The signal of IHA were compared to normal cerebral grey matter. The presence of brain malformations were recorded in five broad categories of grey matter heterotopia, midline defects, brainstem anomalies, cerebellar anomalies, focal cortical dysplasia and cerebral ventriclular dysplasia.
Results: A total of 16 cases of IHA were identified. Of these 56% (9/16) were male with patients ranging from day 1 of life to 7 years of age at the time of scanning (mean age 2.6 years).

Grey matter heterotopia was associated with IHA in all cases (100%). Midline abnormalities were present in 87.5% (14/16) cases, almost all involving the corpuds callosum. Posterior fossa abnormalities were present in 31.3% (5/16). Dilated or dysplastic ventricles were also present in 31.3% (5/16). Focal cortical dysplasia was present in 43.8% (7/16), almost entirely comprised of polymicrogyria. Correlating the signal characteristics of IHA to normal deep and cortical grey matter confirmed that IHA followed grey matter signal on both T1 and T2 sequences in all cases.
Conclusions: In our cohort IHA was seen to be associated with grey matter heterotopia in all cases and these lesions remained isointense to grey matter on all sequences. This raises the possibility of whether these lesions may in themselves represent a previously unrecognised form of grey matter heterotopia. Further studies will be required.