Phakomatoses Flashcards

1
Q

Phakomatoses are characterized by:

A
  • Hamartomas and Congenital Malformations affecting structures of ectodermal origin (visceral organs to a lesser extent)
    • Ectodermal Origin:
      • Nervous system
      • Skin
      • Globe
      • Retina
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2
Q

What are 6 Inherited Cancer Predisposition Syndromes in which exposure to ionizing radiation should be minimized?

A
  • Ataxia-telangiectasia
  • Hereditary retinoblastoma
  • Li Fraumeni syndrome
  • Neurofibromatosis type 1
  • Nevoid basal cell nevus syndrome
  • Nijmegen breakage syndrome
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3
Q

NF1 gene is what?

A

Tumor supressor gene expressed in neurons, schwann cells, oligodendrocytes

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4
Q

Of patients with NF1 - will most develop OPGs?

A

No, only 15%

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5
Q

Of patients with OPGs, do most have NF1?

A

No, 40%

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6
Q

Is unilateral or bilateral involvement of an OPG classic for NF1?

A

Bilateral

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7
Q

What does FASI stand for? How is it defined?

A
  • Focal Area of Signal Intensity - caused by Myelin Vacuolization (layers of myelin become separated as they spiral around the axon)
    • No mass effect,
    • No contrast enhancement
    • No hemorrhage
    • Increased diffusivity on DWI
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8
Q

What is this? Where are they usually found?

A
  • FASI (in NF1) - Focal Area of Signal Intensity
  • Found in globus pallidus, Internal Capsule, Corona radiata, Thalami, Deep cerebellar nuclei.
  • NOT found in subcortical white matter/centrum semiovale
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9
Q

True or false: OGPs in NF1 are more likely to include primary involvement of the optic nerve (vs only the chiasm and optic radiations)

A

True - sporadic cases of OPG are more likely to involve only the chiasm/radiations and have a worse prognosis vs. indolent course of NF1 OPGs involving only optic nerve

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10
Q

Which course of OPG is more indolent: NF1 or sporadic?

A

NF1 (worse prognosis if sporadic)

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11
Q

What is the treatment for OPG in patients with NF1?

A

OPGs are low histological grade (pilocytic astrocytomas). They may even regress in patients with NF1. So - treatment should not be aggressive - wait to see if symptomatic/radiologic progression

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12
Q

How to differnetiate OPG from FASI?

A

OPGs have contiguity, mass effect, low T1 on post-contrast, enhancement after contrast, elevations in choline on MRS

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13
Q

What is an appropriate protocol for assessment of the Orbits in NF1?

A

Hi-res (<3mm) T1 and T2 FS axial/coronal sequences through globes, optic nerves, chiasm, followed by T1 FS - post Gad axial/coronal images. Followed by routine brain.

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14
Q

Where can an OPG extend when beyond the optic pathway?

A
  • superiorly: into hypothalamus, fornices, septum pellucidum
  • Laterally: Temporal lobes
  • Posteriorly: Optic radiations
  • Inferiorly: into crebral peduncles/brain stem.
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15
Q

Is this spectroscopy from a FASI or OPG?

A

OPG (increased choline to creatine ratio)

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16
Q

Gliomas in NF1 other than OPG: What can occur?

A

Basically - any other low or high grade neoplasm, but typically lower grade, ie pilocytic astrocytomas - which can occur almost anywhere - cerebral hemispheres - brainstem (midbrain and medulla are most common) - These tumors are more indolent than in the general population - can usually be watched. Sometimes no treatment until symptomatic progression.

17
Q

What is this in a patient with NF1?

A

An area of FASI that turned into a pilocytic astrocytoma (this is why they need to be followed)

18
Q

What is this in a patient with NF1?

A
  • Pilocytic Astrocytoma (FASI would not enhance or have mass effect)
  • Tumor course is more indolent than in general population - can usually be followed with no tx unless clinically symptomatic
  • Image is of MRS of lesion - Cho/Cr is abnormally high (normal less than 1.5)
  • Naa:Cr is abnormally low (normally greater than 2)
19
Q

What is this in a patient with NF1?

A

Hypothalamic Hamartoma

  • Should not be confused with a glioma
  • Follows gray matter on all sequences; No enhancement
  • With NF1, no association with gelastic seizures or precocious puberty (typically)
20
Q

Why might a patient with NF1 develop hydrocephalus?

A

Usually from a tectal glioma causing mass effect on the aqueduct

21
Q

What is the typical progression of FASIs?

A

Lesions appear during late infancy, with a peak of new lesions b/w 6-12 years old. Lesions then regress and are almost never seen after 20 years old.

22
Q

Why do FASIs regress?

A
  • Maybe due to remyelination or myelin repair.
23
Q

Is there abnormal diffusivity in all of the white matter in NF1 - even if it looks normal?

A

Yes - abnormally increased, maybe related to abnormal myelination and subtle myelin vacuolization (one of the genes for correct myelination within the oligodendrocyte cell is embedded within the NF1 gene)

24
Q

When should FASIs be followed if there is concern for tumor? And what would we be looking for?

A

6 months to a year - Enlargement, Mass effect, Enhancement, Reduced diffusion in solid portion, Increased blood volume, Increased Choline, Decreased Cr and NAA on MRS

25
Q

In NF1, why are areas of FASI like Globus Pallidus and Thalamus sometimes also bright on T1

A

Thought to represent increased or remyelination (sort of repair after vacuolization) - typically occurs after T2 prolongation first appears and tends to persist after T2 prolongation disappears.

26
Q

In NF1 - is increased T2 signal in the hippocampi worrisome?

A

No - This is not progressive. Hippocampal volume is normal or increased (as opposed to mesial temporal sclerosis) - is not progressive.

27
Q

What does this person likely have?

A

NF1 - large CC due to increased myelination (maybe after repair?) or redundancy of fibers after decreased apoptosis?

28
Q
A