Hypothalamic Hamartoma

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.


Hypothalamic Hamartoma

What is a hypothalamic hamartoma?

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.


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Are there different types of hypothalamic hamartomas?

Healthcare providers usually categorize HH by its location in the hypothalamus and the types of symptoms it causes. The two categories of HH include:

  • Central precocious puberty: Growths form near the front of the hypothalamus where it meets the pituitary gland. They can affect hormone levels and lead to early puberty and sexual development.
  • Epilepsy and related neurobehavioral symptoms: Growths form toward the back of the hypothalamus. This is where it connects to your brain’s third ventricle (the space between the lower left and right sides of your brain). They can disrupt electrical activity in your brain and cause seizures and abnormal behavior.

About half of the people with HH have symptoms of both precocious puberty and epilepsy.

Who gets hypothalamic hamartomas?

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.


How common are hypothalamic hamartomas?

HH is rare. Studies vary, suggesting it occurs in about 1 in 100,000 to 1 in 200,000 children.

Symptoms and Causes

What causes hypothalamic hamartomas?

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.


What are the symptoms of hypothalamic hamartomas?

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:

  • Acne.
  • Breast development in girls.
  • Deep voice.
  • Early menstruation in girls.
  • Mature reproductive organs, including enlargement of the testicles, scrotum and penis in boys.
  • Pubic hair.
  • Short height.

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:

  • Atonic seizures, or drop attacks, which cause sudden muscle weakness or falls.
  • Dacrystic seizures, which resemble crying.
  • Tonic-clonic seizures, which cause loss of consciousness and violent body movements.

The following neurological symptoms of HH, which tend to get worse over time, usually accompany epilepsy:

  • Behavioral issues, such as aggression or periods of rage.
  • Developmental delays.
  • Intellectual disabilities, including problems with reading, writing or doing math.
  • Problems with memory, thinking and other cognitive skills.

Diagnosis and Tests

How are hypothalamic hamartomas diagnosed?

HH can be hard to diagnose for a few reasons:

  • Neurobehavioral symptoms can resemble other conditions such as oppositional defiant disorder and attention-deficit/hyperactivity disorder (ADHD). A lot of children with HH also have these disorders.
  • Symptoms such as gelastic seizures might appear early in life, but it’s easy to confuse them with the normal expressions and movements of a baby.
  • The hypothalamus is very small (about the size of a pea) and deep in your brain, so hypothalamic growths may not show up on some imaging exams, such as head CT scans.

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.

Management and Treatment

How are hypothalamic hamartomas treated?

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:

  • Resection surgery: A surgeon may perform brain surgery to remove the hamartoma. They either do a craniotomy to open your skull, or they drill a hole in your skull and insert an endoscope. The endoscope is a thin, flexible tube with a video camera on one end that allows your surgeon to see inside your brain without opening your skull. Your surgeon funnels surgical tools through the endoscope and removes the growth.
  • Stereotactic radiofrequency thermoablation: This form of ablation therapy uses heat to treat the hamartoma. A surgeon inserts thin probes through your skull until they reach the growth. They use radio waves to heat the probes and destroy the tissue. Results are usually immediate, but some people need multiple procedures if the growth is large.
  • Stereotactic laser ablation: This minimally invasive option destroys the tumor using a laser light that is delivered via fiber optic cable. It can be used alone or in combination with other types of therapy.
  • Gamma Knife® radiosurgery: This treatment is a form of radiation therapy. It uses powerful beams of energy to destroy the tumor. It may take between six months to several years for full results to take effect, so it’s better for patients whose symptoms aren’t severe. Gamma Knife surgery isn’t actually surgery, so it doesn’t require an incision (cut in your skin). But you may need to wear a frame on your head that’s attached to your skull with pins.

What are the risks of hypothalamic hamartomas treatment?

As with any surgery, these procedures carry risks of bleeding, infections or reactions to anesthesia. Additional risks include:


How can I prevent hypothalamic hamartomas?

There’s no way to prevent HH.

Outlook / Prognosis

What’s the prognosis (outlook) for people with hypothalamic hamartomas?

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:

  • Are very young when seizures start.
  • Have frequent seizures.
  • Have large hamartomas.

Living With

What questions should I ask my doctor?

If you have HH, you may want to ask your doctor:

  • What type of treatment is best for me?
  • How likely is it that I’ll need multiple treatments or surgeries?
  • What should I do to manage the side effects of treatment?
  • How will treatment affect my ability to work, go to school and perform normal activities?

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.

Medically Reviewed

Last reviewed on 11/10/2021.

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