Neurosurgery notes/Anatomy/Cerebellum/Cerebellar clinical presentation/Posterior fossa syndrome

Posterior fossa syndrome

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Cerebellar clinical presentation

Cerebellar mutism

General information

  • AKA
    • Mutism with subsequent dysarthria
  • There is also akinetic mutism arising from Corpus callosotomy
  • Definition:
    • Speechlessness that develops following various cerebellar injuries
      • Cerebellar trauma
      • Stroke
      • Haemorrhage
      • Viral cerebellitis
      • Post-resection of posterior fossa brain tumours (most common)
        • Essentially always improves, but almost never back to normal.
  • Cerebellar mutism (CM) may occur in isolation, or may be encountered as part of other more global syndromes that involve the posterior fossa:
    • Cerebellar mutism syndrome:
      • CM, ataxia, hypotonia & irritability, which may be encountered as part of…
    • Posterior fossa syndrome:
      • Cerebellar mutism syndrome+ cranial nerve deficits, neurobehavioral changes & urinary incontinence or retention
  • CM is not part of the cerebellar syndrome: ataxia, dysmetria & nystagmus.

Numbers

  • Children: 11–29% following surgery for cerebellar tumours
    • Medulloblastoma (53%)
      • Risk factors for medulloblastoma
        • Brainstem involvement
        • Midline location
    • Ependymoma (33%)
    • Pilocytic astrocytoma (11%)
  • Adults: Post-op CM has been observed in ≈ 1% of adults following p-fossa surgery.

Risk factor

  • Damage the Superior cerebellar peduncle and periaqueductal area almost 100% will get mutism.
  • Midline tumours: medulloblastoma
  • Brainstem infiltration
  • Young age

Pathophysiological

  • Still unknown
  • Theories include:
    • Vasospasm
    • Cerebellar ischemia
    • Cerebellar oedema
    • Transient dysregulation of neurotransmitter release.
    • Cerebellar diaschisis (from the Greek: "shocked throughout”):
      • Most accepted theory
      • Metabolic hypofunction in a brain region distant but connected to an area of brain injury.
        • Disruption of Cerebello-cerebral circuits such as:
          • Dentate-rubro-thalamo-cortical (DRTC) tract
            • Which originates in the dentate nucleus, extends through the superior cerebellar peduncle, and decussates to the contralateral cerebral hemisphere, where it connects the ventrolateral nucleus of the thalamus to diverse cortical areas.
            • See cerebellar anatomy
          • SPECT scans demonstrated transient reduction of cerebral perfusion in frontal, parietal & temporal cortices of patients with post-op CM.
          • In this manner, a supratentorial condition is provoked by disruption of connections to the cerebellum as a result of cerebellar injury.

Clinical features

  • Consists of diminished speech output, hypotonia, ataxia, and emotional lability.
  • Delayed onset (mean: 1.7 days post-op, range: 1–6 days)
    • Is initially fine in the first few days postoperatively develops mutism without any corresponding focal neurological signs.
    • The deficit usually recovers
      • Few weeks to 6 months with an immediate return of full words and sentences.
    • Resolution of the muteness is often followed by a period of dysarthria, and more recent studies have demonstrated that persistent impairment of motor speech is common and complete recovery of speech and language is infrequent.
  • Limited duration (mean: 6.8 weeks, range: 4 d–4 months),
  • Long-term linguistic sequelae (in 98.8% of patients).

Management

  • Treatment: supportive measures:
    • Speech & rehabilitation therapy.
  • Prevention:
    • Avoiding midline splitting of the cerebellar vermis (e.g. by using the telovelar approach to the 4th ventricle).
    • However, results are conflicting and general recommendation for surgical strategies to avoid CM cannot be made at this time.

Outcome

  • 50% who develop mutism will have permanent inability to walk for the rest of their life
  • Mutism seen in children usually 1–4 days after a vermian lesion resection that may take weeks to months to resolve

Cerebellar cognitive affective syndrome

  • Predominantly in adults
  • Impairments of executive function
  • Personality change with blunting of affect or disinhibited and inappropriate behaviour
  • Left cerebellar injury → visual-spatial defects
  • Right cerebellar injury → linguistic processing
    • Visual-spatial disorganisation and impaired visual- spatial memory
    • Difficulties with language production including
      • Dysprosodia (Dysprosody)
        • Prosody refers to the variations in melody, intonation, pauses, stresses, intensity, vocal quality, and accents of speech
        • Why abnormal pt speaks in an accent which is not their own. However, dysprosody can also manifest itself in other ways, such as changes in pitch, volume, and rhythm of speech
      • Agrammatism
      • Mild anomia

Differences

Cerebellar mutism
Cerebellar cognitive affective syndrome
More transient symptoms
More chronic symptoms
Kids>adults
Adults>kids