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What

Diencephalic syndrome (DS) is a rare disorder resulting in severe emaciation (extreme weight loss) of infants and young children. This weight loss – often referred to as “failure to thrive” – occurs along with a loss of nearly all body fat and takes place despite normal appetite and food intake. In most cases, DS occurs in association with a tumor at the base of the brain near the hypothalamus (the part of the brain that is believed to control appetite and weight gain). The word “diencephalic” refers to the diencephalon, the part of the brain that develops into the hypothalamus.

Who

Diencephalic syndrome affects slightly more males than females, but the incidence of the disorder is quite low in all populations. Symptoms usually first arise between 6 and 12 months but may first appear as late as 2 or 3 years of age. At this point, no difference has been found in disease rates among individuals of different ethnic backgrounds. It is not known exactly how common the disease is, but it is believed to be extremely rare with only a few hundred cases ever reported in the medical literature.

Signs and Symptoms

In most cases, infants and children with diencephalic syndrome first experience extreme weight loss or the inability to gain weight. At the same time, however, the height, growth rate, and head circumference of these children are generally normal. The weight loss cannot be corrected by increasing the amount that the child is fed. Despite their emaciated state, children with DS have normal or even higher than normal intelligence. Children with this disorder are usually described as happy and social children who have met all developmental milestones before or at appropriate ages. Over time, they may develop symptoms such as vomiting, abnormally increased muscular activity or hyperactivity (known as “hyperkinesias”), paleness, abnormal twitching eye movements (called “nystagmus”), and a euphoric disposition.

Possible Causes

The symptoms of diencephalic syndrome are due to the effects of a tumor on the hypothalamus and nearby parts of the brain. The tumor presses against these important brain structures, leading to the emaciation and other problems associated with the disease. It is unclear why these tumors form and why some tumors in this area cause DS and some do not. Most tumors that cause the disease are approximately 3 cm by 3 cm and are in a class of tumors known as astrocytomas. There does not seem to be a genetic cause for diencephalic syndrome, but more research in this area is necessary.

Diagnosis

There is no single lab test or procedure that can be done to definitely determine if a child has diencephalic syndrome. Instead, it must be considered whenever a young child has unexplained failure to thrive. Most routine lab tests are normal in children with DS, regardless of their ill appearance. In many such children, however, amount of growth hormone (GH) in the blood may be abnormally high so it is important to check these levels. The presence of a tumor at the location usually associated with DS can be checked via either magnetic resonance imaging (MRI) or computed tomography (CT), with MRI being the preferred mode of tumor detection.

Treatment

There is some disagreement regarding the best way to treat children with diencephalic syndrome. Theoretically, the best way to treat children with DS would be to completely remove the tumor, as this would allow the hypothalamus to regain normal function and effectively “cure” the child. In most cases, however, complete removal of the tumor is impossible because it is so deep within the brain. Surgically removing the tumor would require damaging other important areas of the brain. Removing part (but not all) of the tumor is generally somewhat easier, but with any surgery of this type, there is a great risk of irreversibly damaging the brain. Radiation therapy (the use of powerful x-rays to destroy unwanted cells, such as tumors) can also effectively eliminate the tumor, but this type of therapy can also harm normal brain tissue. Chemotherapy (the use of strong medications to kill abnormal cells, such as those of a tumor) is currently being studied as a possible therapy for children with diencephalic syndrome. More research is necessary, but preliminary reports show that chemotherapeutic drugs may help children with DS gain weight without causing negative side effects. It also seems to minimize the need for additional types of treatment. Children with diencephalic syndrome must be monitored carefully by a team of physicians including an oncologist, as the hypothalamic tumor has high metastatic potential. This means that there is a danger that the tumor will spread to other parts of the body and cause further damage. This risk can be lessened with careful medical supervision.

Prognosis

The prognosis for individuals with diencephalic syndrome varies widely. Without any treatment, children usually live for only 1 to 2 years, but some have survived up to 12 years after the diagnosis. With treatment, however, the outcome can be much better. As mentioned above, there is no consensus regarding the best treatment for children with DS, but surgery, radiation therapy, chemotherapy, and any combination of these three can be beneficial. If the tumor can be completely destroyed, children diagnosed with diencephalic syndrome can gain weight and live normally to adulthood. Research shows that the tumors associated with DS tend to be unusually malignant (meaning that it is very possible that they will spread to other parts of the body), so care must be taken to monitor for tumor metastasis. These hypothalamic tumors, if not carefully watched, have been known to spread to the spinal cord and elsewhere in the body, potentially killing the patient. With careful monitoring and proper treatment, however, children with diencephalic syndrome have a good chance of living full and lengthy lives.

Connect with other parents

In the spirit of community and support, Madisons Foundation offers the unique service of connecting parents of children with rare diseases. If you would like to be connected to other parents of children with this disease, please fill out this brief form.

Weblinks

WebMDHealth: Diencephalic Syndrome
Unfortunately, there are very few good resources on the internet about diencephalic syndrome. This site is a brief and easy-to-understand description of the disease with contact information for various groups and organizations that may be of assistance to families affected by the disorder. The following websites provide information about astrocytomas:

American Brain Tumor Society
This is an excellent site for both patients and health professionals. Offers comprehensive information pertaining to tumors, treatment and clinical trials, as well as additional resources and support services. Has a special link for kids.

The Brain Tumor Society
Another thorough site devoted to education, research and support.

National Brain Tumor Foundation
This organization is focused on offering support services. The site invites patients and their families to participate in the nationwide Angel Adventures.

Google Search for Diencephalic Syndrome

References and Sources

Ertem D, et al. (2000) An Uncommon and Often Overlooked Cause of Failure to Thrive: Diencephalic Syndrome, Journal of Pediatric Gastroenterology and Nutrition, 30(4), p 453-7. Fleischman A, et al. (2005) Diencephalic Syndrome: A Cause of Failure to Thrive and a Model of Partial Growth Hormone Resistance, Pediatrics, 115(6), p e742-8.