Skip to content

Benign Parietal Thinning

Summary

fleuron

  • Benign parietal thinning is a focal thinning of the parietal bone, typically bilateral and symmetrical
  • Asymptomatic condition, often discovered incidentally on imaging studies
  • No intervention required; important to differentiate from pathological conditions1

Pathophysiology

  • Exact etiology remains unclear
  • Hypothesized mechanisms:
    • Congenital developmental variation
    • Age-related bone resorption
    • Hormonal influences, particularly in postmenopausal women
  • Characterised by focal thinning of the outer table and diploe, with preservation of the inner table

Demographics

  • More common in older adults, typically over 60 years of age
  • Higher prevalence in females, particularly postmenopausal women
  • No known racial or ethnic predisposition
  • Estimated prevalence of 0.4-1.3% in the general population

Diagnosis

  • Usually an incidental finding on imaging studies
  • Clinical presentation:
    • Asymptomatic
    • No associated neurological deficits or palpable abnormalities
  • Differential diagnosis:
    • Metastatic lesions
    • Multiple myeloma
    • Hyperparathyroidism
    • Fibrous dysplasia
    • Paget's disease

Imaging

  • CT:
    • Bilateral, symmetrical focal thinning of the parietal bones
    • Typically located in the parasagittal region
    • Sharply demarcated margins
    • Preservation of the inner table
    • No associated soft tissue mass or bone destruction
  • MRI:
    • T1 and T2 signal intensity similar to normal bone marrow
    • No contrast enhancement
  • Skull radiographs:
    • May show focal lucencies in the parietal region
    • Less sensitive than CT for detection and characterization

panels-1

  • Incidental finding of thinning of the parietal bone with loss of the outer cortex that was stable over at least 5 years.
  • The patient was systemically well with no clinical or laboratory evidence of a haematological disorder.

Treatment

  • None required; recognition avoids mistaking it for a destructive lesion

Differential diagnosis

Imaging differential Differentiating feature
Lytic metastasis / myeloma Asymmetric, permeative or "punched-out" lucencies with a soft-tissue component and inner-table destruction
Parietal skull fracture Sharp linear lucency without smooth thinning; overlying scalp swelling
Parietal foramina Well-corticated defects, usually paired and more posterior

  1. Sanati-Mehrizy et al. Characterization of Bilateral Parietal Thinning. 2020. The Journal of craniofacial surgery - Open in new tab. ↩