Absent Septum Pellucidum

Absent Septum Pellucidum

It is rare to find babies born without the septum pellucidum (SP), which is part of the structure of the brain. The septum pellucidum is a thin membrane is normally positioned in the middle of the brain separating the two halves of the brain. It is connected to a cluster of nerve fibres, called the corpus callosum, which connects the cerebral hemispheres and transfers information between them.

Absence of the septum pellucidum accompanies a range of brain malformations that affect the neurodevelopmental process, behaviour, and intelligence. In some cases, seizures occur. Babies who are born without the septum pellucidum and also have certain abnormalities such as abnormal development of the optic disk and pituitary deficiencies, have a disorder called septo-optic dysplasia.

Typically, an absence of the membrane is not an isolated finding as it would normally be associated with other disorders such as septo-optic dysplasia. Symptoms of a missing septum pellucidum may include changes in vision, seizures, behavioural changes, and learning difficulties. And treatment will depend largely on the underlying disorder.

The National Organization for Rare Disorders (NORD) is dedicated to providing assistance for those with rare conditions like this and March of Dimes aims to prevent birth defects.

Epidemiology

The septum pellucidum is partially or completely absent in two or three babies in every 100,000.

Diagnosis

Absence of the septum pellucidum can be diagnosed through imaging like an MRI. A diagnosis can be made prenatally, that is, before the child is born. However, symptoms of the abnormality typically present during childhood. If it is discovered that an individual does not have the septum pellucidum, there must be a further probe for any underlying disorders. While it is possible for the missing septum pellucidum to be an isolated finding, that is very rarely the case.

Cavum septum pellucidum is expected to be visualised anywhere from 18 to 37 weeks and within a biparietal diameter of 44 to 88 millimetres. There must be further investigation if it is not detected within that time interval. Meanwhile, if the septum pellucidum is seen to be absent on the ultrasound exam either after 37 weeks or before 18 weeks, that would be a normal finding.

Pathology

Absence of the membrane may be acquired secondary to another pathological process or it may be developmental.

Symptoms

The membrane’s function is to provide information about how the body is doing to the rest of the body. That information may include details such as how safe the environment is, whether the body has received enough food, or whether the body is well rested. Therefore, a person with a missing septum pellucidum may feel tired even when they are well rested or hungry when they are not. In some cases, individuals with missing the septum pellucidum have a high body mass index (BMI) or do not grow very tall.

Usually, the symptoms of an absent septum pellucidum vary, but it is often difficult to determine which symptoms are due to the missing membrane and which are due to the underlying disorder. The symptoms most commonly seen include:

  • Blindness
  • Developmental delay
  • Dilated pupils in light
  • Hormonal problems
  • Impaired intelligence
  • Inward deviation of eyes
  • Jaundice
  • Learning disabilities
  • Low muscle tone
  • Mental retardation
  • Neurological problems
  • Nystagmus
  • Outward deviation of eyes
  • Reduced vision
  • Seizures

Causes

A missing septum pellucidum may be the result of a combination of many different factors depending largely on the underlying condition. Some individuals are born with a fluid build-up in the brain, called hydrocephalus, and others may develop it. The excess fluid can result in the disintegration of the septum pellucidum if the build-up is not treated.

In some cases, absence of the septum pellucidum is due to a genetic condition the baby is born with. Some individuals are born without a corpus callosum, which is the collection of nerves connecting the cerebral hemispheres. In such cases, the person will also be born without a septum pellucidum.

Other causes include:

  • Corneal abrasion or ulcer
  • Herpes simplex or zoster infection
  • Ischemic optic neuropathy
  • Ocular onchocerciasis (“river blindness”)
  • Retinal detachment
  • Transient vision loss
  • Vitreous or aqueous haemorrhage (hyphema)

Prognosis

An absent septum pellucidum by itself, is not a life-threatening condition, but in cases where the missing septum pellucidum is a characteristic of septo-optic dysplasia, the prognosis will vary according to which associated symptoms are present and how severe they are.

Treatment

Since absence of the septum pellucidum in and of itself is not a disorder but is usually a characteristic seen in persons with septo-optic dysplasia, treatment will be focused on the underlying condition.

Absence of the septum pellucidum is commonly treated symptomatically and supportively. Treatment of the condition will depend on the case and its peculiarities. AV fistula will have to be embolised, cataracts will be removed surgically, cavernous sinus thrombosis will be treated with antibiotics and anticoagulation, glaucoma will be treated with topical anti-glaucoma medications and peripheral iridotomy for angle closure, herpes zoster will be treated with systemic acyclovir, and keratoconus/corneal hydrops will be treated with cycloplegics, hypertonic (5%) NaCl ointment, or corneal transplant.

In cases where mucormycosis is a problem, treatment may include amphotericin B and debridement, nonarteritic ischemic optic neuropathy will be treated with aspirin, optic neuritis will be treated with systemic steroids, pituitary apoplexy will be treated with systemic steroids and neurosurgical intervention, retinal detachment will be treated by surgical repair, temporal arteritis will be treated with systemic steroids, and tolosa-hunt will be treated with systemic steroid.

Other underlying causes such as hypotension, carotid stenosis, brain tumours, and cardiac valvular vegetations will be treated accordingly.

What does absent septum pellucidum mean?

Absent septum pellucidum is a disorder where a person is born without the septum pellucidum.

Where is the septum pellucidum located?

The septum pellucidum is positioned in the midline of the brain between the two halves of the brain.

What is the function of the septum pellucidum?

It provides information about the body to the other parts of the body.

Can absence of the septum pellucidum be treated?

Yes.

Can the septum pellucidum be developed after birth?

Yes.

Please find detailed answers here.

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