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Diencephalic Syndrome

Last updated Aug. 24, 2018

Approved by: Krish Tangella MD, MBA, FCAP

Diencephalic Syndrome is a rare neurological disorder caused by a tumor located in the diencephalon, an area of the brain that contains the thalamus and hypothalamus.

What are the other Names for this Condition? (Also known as/Synonyms)

  • Diencephalic Syndrome of Childhood
  • Diencephalic Syndrome of Emaciation
  • Russell’s Syndrome

What is Diencephalic Syndrome? (Definition/Background Information)

  • Diencephalic Syndrome is a rare neurological disorder caused by a tumor located in the diencephalon, an area of the brain that contains the thalamus and hypothalamus
    • The hypothalamus controls the pituitary gland; and together they are responsible for a vast amount of hormonal control in the body
    • The hypothalamus also regulates hunger, thirst, sleep, and body temperature
  • The tumor causing Diencephalic Syndrome is often located near the optic chiasm. This area of the brain contains the nerves that run towards the back of the brain from the optic nerve
  • Diencephalic Syndrome is often characterized by a failure to thrive or the inability to gain or maintain fat tissue (hence leading to emaciation). The complications related to the syndrome can be severe and even life-threatening
  • Chemotherapy, surgery, and radiation therapy are the most common treatments used to treat the tumor responsible for Diencephalic Syndrome. The prognosis of this disorder is dependent upon the severity of the condition, but is generally guarded

Who gets Diencephalic Syndrome? (Age and Sex Distribution)

  • Diencephalic Syndrome onset usually begins in early childhood or infancy. It is rarely reported in older children or adults
  • The condition affects both males and females
  • All races and ethnic groups can be affected by Diencephalic Syndrome

What are the Risk Factors for Diencephalic Syndrome? (Predisposing Factors)

Diencephalic Syndrome is an abnormal growth of tissue (or tumor that may be benign or malignant), which forms in the diencephalon region of the brain. No clearly identified risk factors are presently noted for this condition.

However, the common risk factors for such type of tumors in the brain include:

  • Genetic factors can play a large part in an individual’s susceptibility to tumor formation
  • Poor diet and lack of exercise have also been linked to tumor formation
  • Radiation exposure can also increase the risk

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others. 

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Diencephalic Syndrome? (Etiology)

Diencephalic Syndrome is caused by a tumor located above the brainstem in the diencephalon region of the brain. The tumors that cause Diencephalic Syndrome may be associated with growth hormone resistance resulting in characteristic weight loss, in spite of adequate calorie intake.

The tumors responsible for the condition may include:

  • Astrocytoma: It is a type of tumor often associated with Diencephalic Syndrome, arising from supportive tissues in the brain
  • Glioma: It is another type of tumor that may be associated with Diencephalic Syndrome, manifesting from glial cells which surround and support the neurons
  • Hypothalamus or optic chiasm gliomas may be due to neurofibromatosis 1, a rare genetic disorder causing multiple, benign (non-cancerous) skin or nerve tumors
  • The tumor related to Diencephalic Syndrome may be unclassified, although this is rare

In extremely rare cases, the tumor may be any of the following:

  • Ependymoma (tumor of the central nervous system tissue)
  • Dysgerminoma (germ cell tumor)
  • Ganglioma (a central nervous system tumor often associated with the temporal lobes)

The exact cause of signs and symptoms due to Diencephalic Syndrome, caused by these tumors, is not yet fully understood.

What are the Signs and Symptoms of Diencephalic Syndrome?

The signs and symptoms of Diencephalic Syndrome can vary widely from one individual to another, and these symptoms include:

  • Prolonged absence of weight gain is commonly observed: Loss of body fat (emaciation) despite a healthy caloric intake may be a sign of Diencephalic Syndrome. However, linear growth may still be achieved
  • Restlessness, hyperactivity, hyper-alertness, and euphoria (intense happiness) have been described in the affected children
  • Sudden, involuntary eye movements (nystagmus) may be present
  • Paleness, vomiting, or headaches may be certain non-specific symptoms
  • Degeneration of the optic nerve may occur (optic nerve atrophy); optic nerve atrophy can lead to vision loss
  • Infants with Diencephalic Syndrome may develop hydrocephalus, a buildup of cerebrospinal fluid in the brain:
    • Hydrocephalus can lead to a variety of symptoms including abnormal swelling in the head or swelling in the optic disc (located on the retina)
    • Increased intracranial pressure

Rare symptoms of Diencephalic Syndrome may include:

  • Low blood sugar
  • Excessive sweating
  • High blood pressure
  • Swelling in hands and feet

How is Diencephalic Syndrome Diagnosed?

A diagnosis of Diencephalic Syndrome is made by the following observations and tests:

  • A physical examination and medical history: The physician performs a physical examination looking for symptoms such as:
    • The child looks emaciated or fails to thrive despite a healthy caloric intake
    • Normal development and growth is followed by prolonged weight loss without any signs of digestive tract problems
  • Imaging techniques:
    • Computerized tomography (CT) scans, showing detailed cross-sectional images of the diencephalon to look for a tumor
    • Magnetic resonance imaging (MRI) scan may also be used to create a cross-sectional view of the diencephalon, to look for a tumor
  • Tests may be run on the cerebrospinal fluid to show elevation of certain proteins or the presence of abnormal cells, which may be indicative of Diencephalic Syndrome

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Diencephalic Syndrome?

Possible complications associated with Diencephalic Syndrome include:

  • Deterioration of the optic nerve (optic atrophy) associated with Diencephalic Syndrome that can result in blindness
  • Severe buildup of cerebrospinal fluid (CSF) can pose a serious threat to normal physical and mental growth of the baby
  • A sudden increase in pressure in the skull or on the brain can lead to an emergency medical situation
  • Although it is rare, Diencephalic Syndrome in adults may become associated with memory loss, disorientation, and psychological disorders

In some cases, a tumor in the diencephalon may be fatal.

How is Diencephalic Syndrome Treated?

Treatments for Diencephalic Syndrome are often directed towards specific symptoms. Treatments vary based on tumor size, tumor location, disease stage, presence or absence of symptoms, age, and health status. Coordinated efforts between specialists may be necessary to come up with a treatment plan, which may include:

  • Low-grade tumors in children have been treated with biological remedies
  • Surgery aimed at removing as much of the tumor as possible (resection)
  • Radiation therapy can be used to kill the tumor cells; however, this is avoided in children under 5, due to an increased risk of adverse side effects
  • Chemotherapy may be administered, especially in individuals with low-grade tumors. It is often administered following radiation therapy to kill the remaining tumor cells

How can Diencephalic Syndrome be Prevented?

There are currently, no known definite preventative measures for Diencephalic Syndrome.

What is the Prognosis of Diencephalic Syndrome? (Outcomes/Resolutions)

The prognosis for individuals with Diencephalic Syndrome may vary and are as follows:

  • Tumors associated with Diencephalic Syndrome are often indolent (arising without any major symptoms) and grow slowly. These tumors may be stable for several years
  • If there is fluid accumulation within the tumor; the tumor may enlarge in size making the prognosis worse
  • Individuals with Diencephalic Syndrome often have long survival. The prognosis is complicated due to the fact that individuals may have longstanding visual problems and dysfunction of the hypothalamus (a part of the brain that controls important functions of the body)
  • Tumors responsible for Diencephalic Syndrome are typically more aggressive than tumors that do not cause the syndrome. In other words, tumors of the brain associated with Diencephalic Syndrome have worse prognosis than tumors of the brain not associated with Diencephalic Syndrome

Additional and Relevant Useful Information for Diencephalic Syndrome:

Tumors associated with Diencephalic Syndrome may be cystic (fluid filled) or solid, which causes compression of the surrounding brain tissue.

What are some Useful Resources for Additional Information?

References and Information Sources used for the Article:

Helpful Peer-Reviewed Medical Articles:

Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: May 10, 2016
Last updated: Aug. 24, 2018