Absent septum pellucidum

Dr Henry Knipe et al.

An absent septum pellucidum may rarely be an isolated finding, or more commonly be seen in association with a variety of conditions.

The septum pellucidum is partly or entirely absent in 2 or 3 individuals per 100,000 in the general population. 

An absent septum pellucidum may be developmental or acquired secondary to another pathological process 1,2

Cavum septum pellucidum is always visualised between 18 and 37 weeks and within a biparietal diameter of 44 to 88 mm. Failure to detect the cavum septum pellucidum within this time interval requires further investigation; however the absence of cavum septum pellucidum on the ultrasound exam prior to 18 weeks, or later than 37 weeks, is considered a normal finding.

Non-visualisation of the septum pellucidum with direct communication of the frontal horns. Additionally the following characteristics may be seen 3:

  • boxing/squaring off of the frontal horns
  • inferior pointing frontal horns
  • abnormally inferiorly positioned fornix (coronal views)
Malformations of the central nervous system
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Article information

rID: 39731
Section: Gamuts
Synonyms or Alternate Spellings:
  • Absent cavum septum pellucidum
  • Absence of septum pellucidum
  • Absence of cavum septum pellucidum

Cases and figures

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    Case 1: semilobar holoprosencephaly
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    Case 2: septo-optic dysplasia
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    Case 3: schizencephaly (open lip type)
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    Case 4: associated with open lip schizencephaly
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    Case 5: apparently isolated
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    Case 6: with polymicrogyria
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