Understanding the path to a proper diagnosis

Diagnostic tools and Early Detection

The diagnosis of HH is based on an individual’s
1) neurological symptoms and 2) radiographic tests.
Early detection can improve the likelihood of a successful treatment outcome. However, it is worth noting here that many of the tools used for diagnosis in the hands of an inexperienced health professional can lead to misdiagnosis and further delay proper treatment. It is highly recommended that any tests be conducted and/or reviewed by individuals with experience in diagnosing and treating individuals with HH.

Neurological and Physical Symptoms

Neurological symptoms can include worsening seizure volume, length and type, decline in learning skills, increased behavior problems, and/or memory deficits. Two other conditions associated with HH that can ultimately lead to its discovery are precocious puberty and Pallister-Hall Syndrome. Precocious Puberty is the most common endocrine condition leading to diagnosis of HH and is defined as unusually early onset of puberty (before age 8 for girls and age 9 for boys). It has been reported as early as infancy. It can occur by itself, without seizures or other neurological problems.

Pallister-Hall syndrome is a less common genetic disorder that affects the development of many parts of the body. Most people with this condition have extra fingers and/or toes (polydactyly) and the skin between some fingers or toes may be fused (cutaneous syndactyly). Pallister-Hall can result in an HH that is often large, however, epilepsy occurs less frequently and is reported to be relatively mild compared to individuals with HH alone.

Magnetic Resonance Imaging (MRI)

Individuals with a possible hypothalamic hamartoma should undergo high-resolution Magnetic Resonance Imaging (MRI) of the brain with special attention to the area of the hypothalamus. Many HH patients have lesions that are missed on initial brain imaging, even when studied with high-resolution magnetic resonance imaging (MRI) because of the inexperience of the person viewing the scans. The MRI scans should be thoroughly scrutinized by someone with HH experience, because these lesions occur deep within the brain, can be small, and are sometimes difficult to detect. HH’s may be as small as a few millimeters to as large as a few centimeters in size.

The preferred protocol for MRI imaging 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.
  • The MRI must include the whole brain cortical evaluation to exclude other causes for seizure.

On-going improvements in MRI screening and a heightened awareness of the hypothalamus as a potential source of seizure activity for patients with epilepsy, should decrease the number of cases that go undetected in the future.

MRI of 15 month old girl with large HH prior to removal (click image for larger view)

MRI-PreOp-2-lrg

MRI of same girl at 3.5 yrs old after HH surgically removed by TC Approach (click for larger view)

MRI-PostOp-2-lrg

Electroencepahalogram (EEG)

While electroencephalograms (EEGs) are commonly used to diagnose other types of seizures, attempts to capture or record gelastic seizure activity by EEG have proven unsuccessful. Scalp EEGs, as well as video EEGs (VEEG), are limited in usefulness as a diagnostic tool because in the early stages of the disorder, the EEG report is quite often normal. This is due to the deep location of the HH and the complex connections of the HH. After some years of seizure activity progression, the EEGs in many patients will show increased activity. Video EEGs are limited because, although a parent can often indicate when a gelastic seizure is occurring and the physical indications may be apparent, there may not be corresponding brain activity indicated on the EEG.

HH Lesion Types

Several attempts have been made to classify HH in order to better understand the characteristics and the impact the HH may have on the surrounding critical structures in that area of the brain. What type of HH you have will be a factor when deciding on a treatment plan.

To properly understand hypothalamic hamartomas, a distinction must first be made between the 2 different subtypes or classifications. They are: 1) intrahypothalamic (or sessile) and 2) parahypothalamic (or pedunculated).

The intrahypothalamic (or sessile) HH has a base of attachment within the third ventricle and can be either partial or complete. These lesions vary significantly in size but typically extend into the third ventricle itself and distort the surrounding anatomical structures, most importantly, the fornix or mammilary body. These structures are critical in the process of memory and behavior and therefore it is common for short-term memory and behavior disturbances to be evident. Sessile HH’s are most often associated with neurological issues and an initial presentation of gelastic seizures with a progression to other seizure types. Just under half of individuals with sessile HH’s will develop precocious puberty at some point in their lifetime. It is not unusual for children with this type of HH to experience a progressive decline in behavior, cognitive abilities, and social skills.

The parahypothalamic (or pedunculated) HH is more often associated with precocious puberty and not usually associated with epilepsy or neurodevelopmental problems. Treatment for these types of lesions is usually aimed at controlling the effects of the sexual development (precocious puberty) and premature bone development. Most cases can be easily classified into one category or the other, but some combinations of the two do exist.

HH is frequently Misdiagnosed

Symptoms ranging from mild to severe seizures can be difficult to recognize. Also, there may be other associated endocrine and behavior issues which may be the first symptoms addressed. In some cases, once the diagnosis of epilepsy or a seizure disorder is made, the next critical step of discovering an HH through high resolution MRI is missed. For some families, gelastic seizures are not readily recognized as a seizure and HH is misdiagnosed as colic, Irritable Bowel Syndrome (IBS), acid reflux, and/or behavioral issues. This can prevent a proper diagnosis and lead to the delay of treatment and in some cases, result in unnecessary procedures.

The importance of working with a medical team familiar with the complexities of HH cannot be overstated. Trust your instincts when dealing with the medical community and always ask questions.

Here are lists of of suggested questions you can print out and take with you to your neurologist, neurosurgeon and/or neuroradiologist.

Here are lists of of suggested questions you can print out and take with you to your neurologist, neurosurgeon and/or neuroradiologist.

Neurologist Questions

Neurosurgeon Questions

Neurosurgeon - Gamma Knife Surgery Questions

Neurosurgeon - Stereotactic Laser Ablation Questions

Make sure you understand their answers and be your own best advocate. 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.