PNS/Neurocristopathies Softchalk

Question 1

Understand the overall division and origin of the nervous system.

Answer 1

Nervous system has two main components
1) Central Nervous System (CNS)- consists of brain and spinal cord and derived mainly from the neural tube itself.
2) Peripheral Nervous System (PNS)- consists of cranial nerves and ganglia, spinal nerves and ganglia, autonomic nerves and ganglia, and the enteric nervous system.
It is is further subdivided into
1)The somatic nervous system
2) The autonomic nervous system, which is divided into
1)The parasympathetic division
2) The sympathetic division
The PNS arises from the neural tube, neural crest cells, and ectodermal placodes.

Question 2

Name the derivatives of the neural crest cells.

Answer 2

Cranial Neural Crest Cells: pharyngeal arch skeletal and connective tissue components, bones of neurocranium, pia and arachnoid mater, parafollicular cells of thyroid, odontoblast, sensory ganglia of CN V, VII, IX, X, parasympathetic ganglia of the head, aorticopulmonary septum.

Trunk Neural Crest Cells: melanocytes, Schwann cells, glial cells in peripheral ganglia, chromaffin cells of adrenal medulla, sympathetic chain ganglia, prevertebral sympathetic ganglia, enteric parasympathetic ganglia of gut, abdominopelvic parasympathetic ganglia.

Question 3

Describe the embryological origin and main clinical characteristics of the neuroblastoma.

Answer 3

This is a neuroendocrine tumor that can arise from any neural crest cell element of the sympathetic nervous system.
Clinical presentation: most present with advanced stage disease, usually with metastasis to bone and marrow.
Often presents with bone pain and limp, it may also present with unexplained fever, weight loss, irritability, and periorbital ecchymosis. Also can present as asymptomatic abdominal mass.

Question 4

Describe the embryological/genetic origin and main clinical characteristics of the neurofibromatosis.

Answer 4

Neurofibromatosis type 1 is an autosomal dominant condition caused by a mutation on chromosome 17.
Clinical Presentation:
-cafe-au-lait spots
-freckles in underarms and groin
-neurofibromas (non-cancerous, benign tumors, usually located on or just under the skin)
-Lisch nodules (spots on the iris that do not cause vision loss
-optic gliomas (tumors that grow along optic nerve, may lead to reduced vision or total vision loss)

Question 5

Describe the embryological origin and main clinical characteristics of the Waardenburg syndrome.

Answer 5

A group of autosomal dominant genetic conditions caused by a variety of mutations on genes that are involved in the development and formation of melanocytes.
Clinical Presentation:
congenital hearing loss
changes in pigmentation of the hair skin and eyes
often have pale blue eyes or different colored eyes

Question 6

Discuss the migration process of neural crest cells.

Answer 6

After the neural crest cells separate from the neural folds or neural tube (called “delamination of neural crest cells”), they migrate to many locations in the body and differentiate. This detachment and migration occurs in a craniocaudal wave–from mesencephalon to the caudal end of the spinal neural tube.

This process occurs before, during, and after closure of the neuropores.

Question 7

Name and briefly describe the main neurocristopathies.

Answer 7

(5) main ones:
- Neuroblastoma (NB): neuroendocrine tumor of any neural crest cell of SYMPATHETIC nervous system
- Schwannoma: benign tumor of Schwann cells, often located near Vestibular branch of CN VIII
- Neurofibromatosis (NF) Type I = Von Recklinghausen disease: Autosomal dominant condition of skin pigmentation and neurofibromas
- Pheocromocytoma: rare tumor in adrenal medulla, mainly in adults 40-60 yo
- Waardenburg syndrome: group of autosomal dominant conditions –> congenital hearing loss and changes in skin/eye pigmentation

Question 8

Describe the embryological origin and main clinical characteristics of Schwannoma.

Answer 8

Schwannoma is a benign tumor of Schwann cells (both Cranial and Trunk neural crest cell origin). Commonly located near vesitbular branch of CN VIII.
Clinical presentation = hearing and balance problems.

Question 9

Describe the embryological origin and main clinical characteristics of Pheocromocytoma.

Answer 9

Pheocromocytoma is a rare tumor in the adrenal medulla (Trunk neural crest cell derivatives). Occurs mainly in adults 40-60 YO.
Clinical presentation = Unexplained hypertension, tremors, anxiety, profuse sweating, pallor, and chest/abd pain.