What is involved in diagnosing HH?

A complete neurological exam and tests are critical steps in sorting out whether a child has a hypothalamic hamartoma (HH) and how it is affecting them. Some key points to consider:

  • The diagnosis of HH is based on an individual’s neurological symptoms and radiographic tests. The condition may look different from one child to the next, depending on how and when different symptoms start.
  • Diagnosing HH early is critical. Too often, the early signs are not detected and people can go years without knowing what is going on. Unfortunately this leads to the person not being treated properly.
  • Specialists with experience in HH should perform and interpret the test results. There are many subtle differences that could lead to a wrong diagnosis and delays in treatment. Proper diagnosis and treatment can make the difference between missing the diagnosis or not.
  • Specialists in HH are most likely found at pediatric epilepsy centers. These organizations can help you find an epilepsy specialist:

What neurological and physical symptoms are seen?

A complete neurological exam helps diagnose seizures seen in HH, as well as other conditions that may be affected by the seizures or be separate problems.

  • Gelastic and dacrystic seizures are usually the first seizure type seen in HH.
  • Over time, more complex and disabling seizures may be seen, such as absence, atonic, tonic, or tonic-clonic seizures.
  • A change or worsening of seizures (such as different types and longer seizures) may occur. Other neurological symptoms may worsen too. For example, learning, behavior, memory, and other cognitive problems are usually more noticeable and worse in people with frequent seizures.

A physical exam can also pick up other conditions associated with HH.

Precocious puberty is the most common endocrine or hormonal problem. Recognizing when this occurs often leads to the diagnosis of HH.

  • Precocious puberty is defined as unusually early onset of puberty. It happens usually before age 8 for girls and age 9 for boys. Yet it has also been reported as early as infancy.
  • It can occur by itself, without seizures, or with other neurological problems.

Pallister-Hall syndrome is a rare genetic disorder that affects how many parts of the body develop.

  • Most people with this condition have extra fingers and/or toes (polydactyly).
  • The skin between some fingers or toes may be fused together (cutaneous syndactyly).
  • This syndrome can result in a large hamartoma. Epilepsy may not be seen as often and may be easier to treat than seizures in people with HH alone.

How are MRI scans used?

People with a possible hypothalamic hamartoma should undergo high-resolution magnetic resonance imaging (MRI) of the brain with special views of the hypothalamus at the base of the brain.

  • Many people have lesions that are missed on initial brain imaging, even when studied with high-resolution MRI, because of the inexperience of the person viewing the scans.
  • The MRI scans should be thoroughly looked at carefully by someone with HH experience, because these lesions occur deep within the brain. The lesions can be small, ranging from a few millimeters to as large as a few centimeters.
  • Improvements in MRI screening and awareness of the hypothalamus as a potential source of seizures may help improve the diagnosis of HH.
  • Special protocols or ways that an MRI scan is done have been developed to make MRI scanning for HH more accurate. The preferred MRI sequence protocol is:
    • Sag T1 – min TE; 3mm slice, 0.5mm gap; FOV 20cm
    • Sag T2(FSE) – 3mm slice; FOV 20cm
    • Cor T2(FSE) – 2 or 3mm; FOV 16cm
    • Cor T1 – 3D SPGR; 2mm slice; FOV 24cm – recon for axial
    • Axial T2(FSE) – routine brain
    • Contrast may be necessary for first evaluation to exclude other lesions. The Sag and Cor T2 are the critical sequences.

Learn more on the Hope of Hypothalamic Hamartomas website.

How are EEGs used to diagnose HH?

While electroencephalograms (EEGs) are commonly used to diagnose other types of seizures, gelastic or dacrystic seizures are hard to pick up on an EEG.

  • In general, scalp and video EEGs may not be helpful in the early stages of HH. EEG tests performed at this time are often normal. This is due to the deep location of the hamartoma and the complex connections or workings of the hypothalamus.
  • Over time, if seizures continue, EEGs in many people will show increased activity.
  • Videos taken during EEG testing may pick up when a gelastic seizure happens. This will give everyone a video recording of the seizure, even if the EEG changes are not seen at the same time.

Why is HH misdiagnosed so often?

Lots of different factors can lead to missing a diagnosis of HH. Here are just a few reasons.

  • Symptoms ranging from mild to severe seizures can be difficult to recognize.
  • Episodes with laughing or crying are often not recognized as seizures. These can be mistaken for colic in a baby, irritable bowel syndrome, acid reflux, or behavioral issues.
  • HH may not be considered when hormonal and behavioral problems are seen.
  • The wrong type of tests may be done or a high resolution MRI is missed.

The importance of working with a medical team familiar with the complexities of HH cannot be overstated.

  • Trust your instincts when dealing with the health care community.
  • Always ask questions!
  • Make sure you understand the answers and be your own best advocate.
  • Get some help. You may have to make some very challenging decisions on your own behalf or that of your child. Ultimately, your treatment plan is up to you and the medical team you trust.
Authored By: 
John F. Kerrigan MD and Sloka Iyengar PhD
Authored Date: 
Reviewed By: 
Ilene Penn Miller and Patricia O. Shafer RN, MN
Friday, March 3, 2017