Neurosurgical lesions

Chiari Malformation

• Congenital abnormalities of the brain characterised by:

o Extension of a tongue of cerebellar tissue into cervical spinal canal

o Caudal displacement of the medulla and inferior part of the 4^th ventricle into the cervical spinal canal

o Frequent association with syringomyelia (or another spinal developmental abnormality)

• Incidence ~0.6% of the population

Type I

Imaging

• >5mm of tonsillar descent

Clinical

• Signs of increased intracranial pressure

o Headache

- usually occipital

- Worse with coughing, positional change or Valsalva

- ?Headache with exertion – unclear association

• Progressive cerebellar ataxia

• Progressive spastic quadriparesis

• Downbeating nystagmus

• Syndrome of cervical syringomyelia (segmental amyotrophy and sensory loss in upper limbs)

• Disorders of the lower cranial nerves

• “Neurogenic cough”

• Can be exacerbated by prolonged hyperextension

• Risk from trauma (e.g. contact sports) is unclear – there are case reports of sudden deterioration, however very low/no incidence of such in registries

Management:

• < 5mm – no further investigation needed

• >5mm with space around cord – consider MRI spine to exclude syrinx, generally no further intervention.

• >5mm and tight or presence of suggestive symptoms – refer for neurosurgery

o Intervention usually only in the case of relevant symptoms.

Type II

• cerebellar tonsillar (>5 mm caudal herniation), brainstem, and fourth ventricle herniation in relation to the foramen magnum

• associated lumbosacral myelomeningocele

There are other types 3-5 which are rare.

Pineal cysts

• 11% of people have one on MRI

• Clinical symptoms

o Vast majority asymptomatic

o Parinaud with hydrocephalus

• Can have a normal solid component

• 99% do not grow

• Management

o If >15mm – consider MRI at 12-24 months, no action if stable.

o Refer if

- Complex cysts/solid tumours

- Hydrocephalus

- Haemorrhage into cysts

- Aqueduct obstruction

Colloid cysts

• Epithelial lines cysts present in 3rd ventricle

• 99% situated at foramen of Munroe.

• Clinical

o Most asymptomatic

o Can cause hydrocephalus

o History of presentation with sudden death – this was all in the pre CT era when there was no imaging follow-up.

• Surgery can cause damage to the fornix with resultant severe memory impairment.

• Risk score to determine need for ongoing imaging

o Factors - Age, size 7mm, FLAIR around ventricle, headache

o Image for 5 years and then only if symptoms.

• Surgery if significant enlargement or hydrocephalus

Pituitary Lesions

25% of people have tumour on autopsy

Pars intermedia cyst – do not have delayed enhancement – benign

Rathke’s cleft cyst – do not enhance

Immune hypophisitis – mimic of tumour, will shrink with steroids