Neurosurgery notes/Paediatrics/Developmental abnormalities/Intracranial Anomalies/Aqueduct stenosis

Aqueduct stenosis

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Intracranial Anomalies

General information

  • Aqueductal stenosis (AqS) produces what is sometimes called triventricular hydrocephalus, characterized by a normal sized 4th ventricle and enlarged third and lateral ventricles on MRI or CT.
  • Most cases occur in children; however some present for the first time in adulthood.

Aetiologies

  • Congenital malformation: may be associated with Chiari malformation or neurofibromatosis
  • Acquired
    • Inflammation (following haemorrhage or infection, e.g. Syphilis, T.B.)
    • Neoplasm:
      • Especially brainstem astrocytomas—including tectal gliomas, lipomas
        • notion image
    • Quadrigeminal plate arachnoid cysts

Aqueductal stenosis in infancy

  • AqS is a frequent cause of congenital hydrocephalus (HCP) (up to 70% of cases), but occasionally may be the result of HCP.
  • Patients with congenital AqS usually have HCP at birth or develop it within ≈ 2–3 mos.
  • Congenital AqS may be due to an X-linked recessive gene.
  • Four types described by Russell:
      1. Forking:
          • multiple channels (often narrowed) with normal epithelial lining that do not meet, separated by normal nervous tissue.
          • Associated with other congenital abnormalities
            • Spina bifida
            • Myelomeningocele
      1. Periaqueductal gliosis:
          • Luminal narrowing due to subependymal astrocytic proliferation
      1. True stenosis:
          • Aqueduct histologically normal
      1. Septum

Aqueductal stenosis in adulthood

  • General information
    • AqS may be an overlooked cause of what may be mistaken as “normal pressure hydrocephalus” in the adult.
    • It is unknown why some cases of AqS would remain occult, and manifest only in adulthood.
    • In one series of 55 cases, 35% had duration of symptoms<1 year, 47% for 1–5 years; the longest was 40 yrs. Although most follow this longstanding benign course, there are reports of elevated ICP and sudden death.
  • Symptoms
      • Headache
        • Most common
        • H/A associated with elevated ICP.
      • Visual changes
        • Blurring or loss of acuity.
      • Endocrine changes
        • Menstrual irregularities, hypothyroidism, and hirsutism.
          •  
      • Symptoms of aqueductal stenosis presenting in adulthood (55 patients, > 16 years of age)
          • Symptom
          %
          H/A
          58
          Visual disturbances
          40
          Mental deterioration
          31
          Gait disturbance
          29
          Frequent falling
          24
          Endocrine disturbance
          18
          Nausea/vomiting
          16
          Seizures
          15
          Incontinence
          13
          Vertigo
          11
          LE weakness
          7
          Hemiparesis or hemianesthesia
          7
          Diplopia
          5
  • Signs
    • Papilledema was the most common finding (53%).
    • Visual fields
      • 22%
      • Reduced peripheral vision, increased blind spots, quadrantic or hemianopic field cuts, or scotomata.
    • Intellectual impairment
      • 36%.
    • Other signs included:
      • ataxia (29%),
      • “pyramidal tract signs” in 44%
      • mild hemi- or para-paresis (22%)
      • spasticity (22%),
      • Babinski’s (20%),
      • Anosmia (9%)
  • Evaluation
    • MRI CISS and CSF Flow studies
      • Demonstrates the absence of the normal flow void in the Sylvian aqueduct.
    • MRI + Contrast
      • R/O tumor.

Treatment (of non-tumoral AqS)

  • Options
    • Shunting:
      • Torkildsen shunt (shunting a lateral ventricle to the cisterna magna) may work in adult cases; however, pediatric patients with obstructive hydrocephalus may not have an adequately developed subarachnoid space for this to function properly
    • ETV
  • Follow-up of at least two years to rule out tumor is recommended.