Tuberous Sclerosis Workup

Updated: Oct 14, 2015
  • Author: David Neal Franz, MD; Chief Editor: Amy Kao, MD  more...
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Workup

Laboratory Studies

Laboratory studies are performed as indicated clinically to identify genetic mutations associated with the disorder, monitor anticonvulsant treatment, identify idiosyncratic or dose-related adverse effects, and identify or monitor underlying renal or pulmonary disease.

Molecular genetic testing is now commercially available in the United States through Athena Diagnostics and at other centers. Testing through Athena was recently extended to include screening for large deletions and other types of mutations, which will improve their diagnostic yield.

Under optimal circumstances, genetic testing identifies mutations in up to 75-80% of affected individuals. Therefore, a negative genetic diagnostic test result does not exclude a diagnosis of tuberous sclerosis.

Diagnosis should be possible in most cases using established clinical criteria. Molecular genetic testing is useful in uncertain or questionable cases, for prenatal diagnosis, and for screening family members of an affected individual. The utility of molecular diagnostic testing is limited by the cost (approximate self-pay costs of $3300 to provide deletion analysis and DNA sequencing for TSC1 and TSC2 index cases and $450 for confirmatory testing in family members). Costs are frequently not covered by private insurance carriers. Patient assistance programs may be available through various laboratories.

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Imaging Studies

Three imaging procedures are usually undertaken: CT or MRI scans of the brain, renal ultrasounds, and echocardiograms. Some centers perform these evaluations annually, at least until adulthood. This is a topic of some controversy, as the natural history of TSC and the cost-effectiveness of these types of screening examinations are not known clearly. Some are concerned that routine screening can lull the clinician into a false sense of security, and thus into ignoring symptoms that arise between serial examinations.

CT or MRI scans of the brain

CT or MRI scans of the brain are performed to identify SEGAs before obstructive hydrocephalus occurs. They also identify the extent and number of cortical tubers present. [2] On occasion, they may reveal vascular dysplastic lesions such as aneurysms.

SEGAs are often large and difficult to resect by the time they produce clinical symptoms; even then, avoiding substantial complications such as blindness, hemiparesis, and shunt dependency may be impossible. Initially their manifestations may be quite subtle, such as a change in personality or behavior. They rarely exhibit significant growth after puberty, if they have not already shown evidence of this. These factors should be considered when planning serial neuroimaging examinations.

The author's own practice has been to perform MRI, rather than CT, scans every 2 years in asymptomatic patients, at least until puberty. In children, sedation usually is required for CT scan, as it is for MRI. MRI is superior to CT scan for detection of tubers, migrational anomalies, and vascular lesions. MRI does not involve radiation exposure, as does CT.

In addition to standard brain MRI protocols, fluid-attenuated inversion recovery sequences (FLAIR) should be obtained. [13] FLAIR is superior for identification of tubers. Contrast can be administered; however, both SEGAs and SENs typically enhance. Contrast enhancement is not in itself an indication that an SEN is going to grow, or that surgical intervention is necessary. MR angiography is useful if an aneurysm or vascular dysplastic lesion is noted.

Some authors have performed resections on SEGAs that exhibit an interval increase in size on serial imaging. Our own practice has been to obtain more frequent imaging studies when a lesion increases in size, provided no signs/symptoms of ventricular obstruction, new focal neurological deficit, or increased intracranial pressure are noted. Lesions may stabilize or stop growing spontaneously after increasing in size (see following images).

Enhancing subependymal nodules, including a probab Enhancing subependymal nodules, including a probable giant cell astrocytoma in the region of the foramen of Monro. Subependymal nodules may increase in size over time from one scan to the next, and then stabilize. This lesion had not changed with serial imaging over 2 years. The patient remains asymptomatic and is monitored closely for any deterioration.
This presumed tuber was first noted in the left fr This presumed tuber was first noted in the left frontal region. It expanded in size, affecting adjacent structures across the midline and resulting in calcifications still evident in the right frontal region. The tuber then spontaneously involuted. About 20% of tubers may show changes in imaging characteristics over time, requiring close imaging follow-up. This patient remained asymptomatic from the mass effect, and his seizures resolved as the lesion involuted.

Renal ultrasounds

Renal ultrasounds are performed to assess change in AMLs or cysts, in the hope that this will allow operative intervention prior to development of renal failure.

Due to under-recognition and underestimation of AML occurrence and size, renal ultrasound is losing favor and is being replaced by abdominal MRI.

Small renal cysts and AMLs usually do not grow significantly until after puberty, and often not until the third or fourth decade of life.

In the author's practice, abdominal MRI is obtained every 2-3 years, concurrent with brain MRI. Studies are obtained more frequently if clinically indicated.

Echocardiograms

Echocardiography is performed as part of the baseline evaluation in a patient with newly diagnosed or suspected TSC. Identification of cardiac rhabdomyomas can aid in diagnosis. Depending on their location and size, rhabdomyomas can result in valvular dysfunction, outflow tract obstruction, ventricular hypokinesis, or arrhythmias.

In our practice, echocardiography is not repeated if no lesions are seen on baseline examination. If cardiac lesions are seen, echocardiography is repeated as indicated clinically.

Positron emission tomography

No current indication exists for routine positron emission tomography (PET) scanning in patients with TSC.

PET scans may be useful when patients are undergoing evaluation as candidates for epilepsy surgery. PET scanning with the tracer alpha-methyltryptophan may have particular utility in identifying epileptogenic tubers as part of the evaluation for epilepsy surgery.

Single-photon emission computed tomography

No current indication exists for routine single-photon emission computed tomography (SPECT) scanning in patients with TSC.

SPECT scans may be useful when patients are undergoing evaluation as candidates for epilepsy surgery.

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Other Tests

Electroencephalogram

EEG should be performed in patients with TSC in whom seizures are suspected. Follow-up EEGs are performed as clinically indicated.

Some patients with TSC have a coexisting recognizable epilepsy syndrome such as West syndrome (ie, infantile spasms) or Lennox-Gastaut syndrome. If so, prolonged video-EEG telemetry may be useful to help in the following:

  • Detecting syndrome-specific EEG findings
  • Capturing and classifying each of the patient's multiple seizure types
  • Educating parents on which of the patient's "events" are seizures and which are nonepileptic behavioral events (especially atypical absences)

Electrocardiogram

Baseline ECG is recommended for all patients newly diagnosed with TSC, since cardiac arrhythmias, although rare, may have sudden death as their presenting symptom.

In the author's practice, ECGs are performed at diagnosis and every 2-3 years thereafter until puberty.

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