A hypothalamic hamartoma (HH) is a noncancerous growth in your hypothalamus, deep in the base of your brain. It can cause hormone imbalances, seizures, cognitive dysfunction and other symptoms. Medication and brain surgery are the most common treatments for HH.
A hypothalamic hamartoma (HH) is a benign (noncancerous) tumor-like growth in your hypothalamus. The hypothalamus is deep in the base of your brain. It maintains homeostasis (stability and balance in our bodies). A mass in the hypothalamus can disrupt many important functions, including:
A hypothalamic hamartoma forms while a fetus develops. It’s congenital, which means the mass is present at birth. It grows as the child’s brain grows, but HH doesn’t spread to other parts of the brain or body. HH usually involves one tumor-like mass, but in some cases, there are several.
Healthcare providers usually categorize HH by its location in the hypothalamus and the types of symptoms it causes. The two categories of HH include:
About half of the people with HH have symptoms of both precocious puberty and epilepsy.
Anyone can get develop HH, but it tends to be more common in males than females. HH primarily affects children and adolescents. But in some cases, people don’t receive a diagnosis until symptoms appear in adulthood.
HH is rare. Studies vary, suggesting it occurs in about 1 in 100,000 to 1 in 200,000 children.
Experts don’t know exactly what causes HH. In about 95% of people, it develops sporadically (without any family history of the disorder). It’s probably the result of a problem with fetal development.
But there may be a link between hypothalamic hamartoma and a genetic disease called Pallister-Hall syndrome (PHS). About 5% of people with HH also have PHS. It’s the result of an abnormal gene and can cause deformities in your hands, feet, larynx (voice box) and anus.
People with HH may show signs and symptoms of central precocious puberty, epilepsy or both.
In some cases, HH doesn’t cause any symptoms.
Central precocious puberty can appear any time before the age of 8 in girls or 9 in boys. It’s possible for symptoms to show as early as the age of 1. Symptoms may include:
Epilepsy can begin in the first year of life, but may be hard to identify until later in childhood. Other neurological symptoms tend to develop between the ages of 4 and 7.
Gelastic seizures are the most common symptom of epileptic HH. These seizures resemble sudden laughter and may happen in very short bursts of just a few seconds. Someone may or may not lose consciousness during a gelastic seizure. These seizures usually go away around the age of 10.
Other types of seizures may include:
The following neurological symptoms of HH, which tend to get worse over time, usually accompany epilepsy:
HH can be hard to diagnose for a few reasons:
The most important diagnostic test for hypothalamic hamartomas is MRI. This imaging exam creates highly detailed images of your brain. Children usually need light sedation so they stay still during an MRI. If they move, the images might not be clear.
Your healthcare provider may also recommend an electroencephalogram (EEG) if you have epileptic HH. This test monitors the electrical activity in your brain while you have seizures. But gelastic seizures can be hard to detect with EEG because HH forms so deep within your brain. The EEG electrodes on your scalp might not pick up the abnormal electrical impulses.
Neurological testing can measure the extent of cognitive problems, such as thinking, learning and remembering. Your healthcare provider may also recommend blood tests to check your hormone levels. These tests may help guide treatment.
Medication is the most common and effective treatment for the symptoms of precocious puberty HH. Monthly injections of a drug that suppresses the release of certain hormones helps keep early puberty symptoms in check. You stop the medication when you reach the normal age for puberty to occur. Most children and teens have a normal puberty and sexual development.
Epileptic HH is more difficult to treat. Gelastic seizures don’t always respond to anti-seizure medications. Until about 20 years ago, healthcare providers thought hamartomas were inoperable (not good for surgery) because they’re in such a sensitive area of the brain. But today, there are highly specialized procedures that can remove the hamartoma without damaging your hypothalamus or surrounding brain tissues.
Your healthcare provider may recommend:
As with any surgery, these procedures carry risks of bleeding, infections or reactions to anesthesia. Additional risks include:
There’s no way to prevent HH.
The outlook for people with precocious puberty HH is good, since medication is so effective at treating symptoms. For epileptic HH, resection surgery is the most effective treatment — about 90% of people experienced fewer seizures after treatment. Thermoablation helps between 67% and 71% of people have fewer seizures. Radiosurgery is effective in about 40% of people.
Cognitive function tends to be worse in people who:
If you have HH, you may want to ask your doctor:
A note from Cleveland Clinic
A hypothalamic hamartoma is an abnormal growth in your hypothalamus, deep in the base of your brain. It can lead to a wide range of symptoms, from hormone imbalances and early puberty to seizures and cognitive problems. Most people can manage hormonal problems with medication, but seizures usually require surgery to destroy or remove the hypothalamic hamartoma.
Last reviewed by a Cleveland Clinic medical professional on 11/10/2021.
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