Neurosurgery notes/Tumours/Cyst and tumour like lesions/Pineal cyst

Pineal cyst

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Cyst and tumour like lesions

Number

  • 20-30 years of age
  • Male to Female ratio=1:3
    • Hormonal changes play a part in their formation.
      • Women get older the cyst initially enlarges and then shrinks.
      • Males, they tend to remain stable over time.
  • 1% of population
    • Common
  • Usual incidental
    • 4% of MRI
    • 25-40% of autopsies
      • As many more are microscopic

Aetiology

  • Obscure and may be due to ischemic glial degeneration or due to sequestration of the pineal diverticulum

Histology

  • Cyst wall:
    • Inner layer: finely fibrillary glial tissue often containing haemosiderin
    • Middle layer: pineal parenchyma with or without calcification
    • Outer layer: thin fibrous connective tissue
  • Cyst contents:
    • Proteinaceous fluid
    • Clear
    • Slightly xanthochromic → hemorrhagic fluid

Clinical Presentation

  • Positional headache
    • Cyst intermittently compress the vein of Galen and/or Sylvian aqueduct
    • Still unproven
  • Enlarge and causes compression 61
    • Aqueductal compression → Hydrocephalus
    • Tectal compression → gaze paresis
      • Including Parinaud’s syndrome
    • Hypothalamic symptoms
  • Pineal apoplexy: Haemorrhage into a pineal cyst can cause rapid expansion

Progression

  • Nonneoplastic, benign
  • Adults: Risk of growing is ≈ 4% with 6 months median follow up
    • PCs <2cm diameter with typical appearance (wall: ≤ 2mm thick and no irregularities or nodular enhancement): are generally considered not to grow, but the natural history is not known with certainty.
  • Children: 11% in children with 10 months median follow-up

Imaging

  • General
    • Like the pineal gland, the walls of pineal cysts do not have a well-formed blood brain barrier → enhance vividly with contrast
    • Well circumscribed fluid density lesions
    • Thin rim calcification seen in 25%.
    • Thin, smooth peripheral enhancement is also often seen.
      • The internal cerebral veins are elevated and splayed by the cyst.
      • 15-20mm in size
  • CT
      • May not be seen due to cyst fluid density similar to CSF
      CT
      CT
      CT+C
      CT+C
  • MRI
    • T1
      • Typically iso/hypointense compared to brain parenchyma
      • 55-60% hyperintense when compared to CSF
      • Usually homogeneous in signal
    • T1 C+ (Gd)
      • 60% enhance
      • Enhancement
        • Usually thin (<2 mm)
        • Smooth
        • Confined to the rim (either complete or incomplete)
      • If post-contrast imaging is delayed (60-90 min) gadolinium may diffuse into the cyst fluid and may lead to the mass appearing solid
      • In atypical cases enhancement may be nodular, or there may be evidence of previous hemorrhage into the cysts
    • T2
      • High signal
      • Usually slightly hypointense to CSF
    • FLAIR:
      • High signal does not often suppress fully
    • DWI/ADC:
      • They demonstrate no restricted diffusion
      Images
      T1
      notion image
       
      T1+C
      notion image
      T2
      notion image
       
      Flair
      notion image
      DWI
      notion image
      ADC
      notion image

Treatment

  • Asymptomatic:
    • 1 yr follow-up MRI if stable then d/c
    • If rapid growth do more fq scans
  • Symptomatic lesions or those that show changes on MRI. Surgery to relieve symptoms and/or to obtain a diagnosis.
  • Hydrocephalus.
    • Surgical options include:
      • CSF diversion:
        • Recommended only for lesions with appearance to typical PC as it does not obtain tissue for pathology.
        • May not relieve gaze disturbance from direct pressure on tectal plate
        • Example:
          • CSF shunt
          • ETV
      • Aspiration only (stereotactic or endoscopic):
        • May not get enough tissue for diagnosis
      • Cyst excision (open or endoscopic):
        • Relieves symptoms
        • Establishes diagnosis
        • Low morbidity

Differential diagnosis

  • Pineal parenchymal tumours
    • Pineocytoma
    • Pineal parenchymal tumour with intermediate differentiation
    • Papillary tumour of the pineal region
  • Epidermoid cyst
  • Arachnoid cyst: these are usually posterior to the pineal gland
  • Germ cell tumours:
    • Germinoma
    • Embryonal carcinoma
    • Choriocarcinoma
    • Teratoma
    • Cerebral metastasis
  • Vein of Galen aneurysm