19 Benign Enlargement of Subarachnoid Spaces


19 Benign Enlargement of Subarachnoid Spaces

Cole T. Lewis, Octavio Arevalo, Rajan P. Patel, and David I. Sandberg

19.1 Case Presentation

19.1.1 History

A 14-month-old female patient presents with a history of macrocephaly and emesis.

19.2 Imaging Analysis

19.2.1 Imaging Findings and Impression

Brain MRI axial T2-weighted (T2w; ▶ Fig. 19.1a,b), axial T2*GRE (gradient recalled echo; ▶ Fig. 19.1c,d), and coronal T1-weighted (T1w) with gadolinium (▶ Fig. 19.1e) images show prominence of the subarachnoid spaces overlying the anterior cerebral convexities (asterisks) consistent with benign enlargement of subarachnoid spaces (BESS) of infancy, which is a normal variant. Note the presence of small bridging veins crossing the subarachnoid spaces (white arrow in ▶ Fig. 19.1e). Lack of susceptibility signal from blood degradation products on T2*GRE images (▶ Fig. 19.1c,d) further supports diagnosis of BESS.

Fig. 19.1 (a–e)

19.3 Differential Diagnosis

  • BESS:

    • Normal transient enlargement of the subarachnoid spaces associated with macrocephaly.

  • Chronic subdural hematoma:

    • It should be suspected if the collection thickness is wider than 6 mm, shows higher T2 fluid-attenuated inversion recovery (FLAIR) signal as compared to cerebrospinal fluid (CSF), and displays hemorrhagic staining on T2*GRE. 1

    • The collection is usually asymmetric, displaces the bridging veins toward the brain surface, and has mass effect.

  • Cerebral volume loss/brain atrophy:

    • When present, it is usually accompanied by small head circumference, and “pointed” forehead due to early metopic suture fusion.

    • Benign enlargement of subarachnoid spaces causes an increase of the head circumference and a flat forehead due to frontal bossing.

  • Acquired communicating hydrocephalus:

    • It usually is caused by a hemorrhagic, inflammatory, or neoplastic process.

    • Some congenital causes include achondroplasia due to narrow foramen magnum and jugular foramina.

    • Density or signal intensity of extra-axial collection does not follow the CSF.

19.4 Diagnostic Pearls

  • Widening of the vertical distance between calvarium and brain frontal parenchyma ≥ 5 mm.

  • It is usually accompanied by enlarged cisterns (suprasellar and suprachiasmatic) and mildly enlarged ventricles (66%).

  • Normal veins are traversing subarachnoid space, the fluid in subarachnoid space follow the CSF signal on all sequences, and there is no abnormal meningeal enhancement. 2 , 3 , 4 , 5 , 6

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Jun 28, 2020 | Posted by in NEUROLOGICAL IMAGING | Comments Off on 19 Benign Enlargement of Subarachnoid Spaces
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