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Carasal

Summary

  • Rare, benign, slow-growing tumour of the carotid body
  • Typically presents as a painless, pulsatile mass in the lateral neck
  • Characteristic "salt and pepper" appearance on CT and MRI imaging

Pathophysiology

  • Arises from paraganglionic cells of the carotid body
  • Located at the carotid bifurcation
  • Highly vascularised tumour
  • Usually non-functional, but may secrete catecholamines in rare cases

Demographics

  • Peak incidence in 5th-6th decades of life
  • Slight female predominance (1.5:1)
  • Bilateral in 10-20% of cases
  • Familial occurrence in 10% of cases, associated with genetic syndromes (e.g., MEN2, VHL)

Diagnosis

  • Often asymptomatic, discovered incidentally
  • Clinical presentation:
    • Painless, slow-growing lateral neck mass
    • Pulsatile on palpation
    • May cause cranial nerve deficits (IX, X, XII) in advanced cases
  • Biochemical testing:
    • Plasma or urinary metanephrines if functional tumour suspected
  • Biopsy generally contraindicated due to risk of haemorrhage

Imaging

  • Ultrasound:
    • Hypoechoic, well-defined mass at carotid bifurcation
    • Splaying of internal and external carotid arteries ("lyre sign")
    • Hypervascular on Doppler imaging
  • CT:
    • Avidly enhancing mass
    • "Salt and pepper" appearance due to flow voids
    • Splaying of carotid bifurcation
  • MRI:
    • T1: isointense to muscle
    • T2: hyperintense with flow voids ("salt and pepper" appearance)
    • Intense enhancement on post-contrast images
  • Angiography:
    • Hypervascular tumour blush
    • Splaying of carotid bifurcation ("lyre sign")
    • May be used for preoperative embolisation

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  • A 50-year-old patient presented with a homonymous hemianopia and motor and sensory disturbance.
  • MRI showed an acute left thalamic infarct on a background of a diffuse leukoencephalopathy affecting the cerebral and capsular white matter, the brainstem and superior cerebellar peduncles.
  • There were no microhaemorrhages.

Treatment

  • Surgical resection is the definitive treatment
  • Preoperative embolisation may reduce intraoperative blood loss
  • Radiotherapy for unresectable tumours or in elderly patients
  • Regular follow-up due to risk of local recurrence
  • Genetic counselling for familial cases

Differential diagnosis

Differential diagnosis Differentiating feature
CADASIL Anterior temporal lobe and external capsule white matter hyperintensities; NOTCH3 mutation; autosomal dominant; no anterior temporal pole sparing
CARASIL Similar confluent white matter pattern; autosomal recessive; HTRA1 mutation; associated with early-onset spondylosis and alopecia
Hypertensive microangiopathy Deep white matter and basal ganglia hyperintensities; associated with poorly controlled hypertension; lacks anterior temporal pole involvement
COL4A1-related small vessel disease Deep cerebral microhaemorrhages; lacunar infarcts; porencephaly; COL4A1/COL4A2 mutations
MELAS Stroke-like lesions not conforming to vascular territories; mitochondrial DNA mutations; elevated serum/CSF lactate
Cerebral amyloid angiopathy Lobar microhaemorrhages; posterior predominance; cortical superficial siderosis; typically older patients
CSF1R-related leukoencephalopathy Confluent white matter disease with calcifications on CT; thalamic involvement; CSF1R mutation
Susac syndrome Corpus callosum "snowball" lesions at the central fibres; sensorineural hearing loss; branch retinal artery occlusions