They are responsible for differentiating into a diverse group of cells that reach different areas of the body. The neural tube and neural crest are derived from the ectoderm; the neural tube goes on to form the brain and spinal cord, while the neural crest cells eventually go on to form various bones and cartilage of the skull and face by migrating through the pharyngeal arches. They also differentiate into the stria vascularis of the cochlea, the nerves and glia of the intestines (myenteric plexus), Schwann cells, which myelinate the peripheral nervous system to allow sufficient conductivity, odontoblasts, which produce dentin deep in the teeth, some neuroendocrine cells, connective tissue around the salivary, lacrimal, pituitary, thymus and thyroid glands, connective tissue of the eye, such as the stroma of the iris and cornea and the trabecular meshwork, and melanocytes, including those in the stroma of the iris that give rise to brown eye colour through melanin. Neural crest cells also have a role in muscle formation, including the wall muscle of certain cardiac arteries. Causes of subtypes
Type 1 is caused by an autosomal dominant mutation in the gene PAX3. PAX3, or paired box 3, is a transcription factor that has a role in maintaining an open window of time for certain neural crest cells (such as those of the head and eyes) to divide and migrate before their terminal differentiation (i.e. to maintain them in the stem-cell state).
A pinealoma is a tumor of the pineal gland, a part of the brain that produces melatonin. If a pinealoma destroys the cells of the pineal gland in a child, it can cause precocious puberty. Signs and symptoms
The pineal gland produces the hormone melatonin which plays a role in regulating circadian rhythms. A pinealoma may disrupt production of this hormone, and insomnia may result.Frequently, paralysis of upward gaze along with several ocular findings such as convergence retraction nystagmus and eyelid retraction also known as Colliers sign and Light Near Dissociation  (pupil accommodates but doesnt react to light) are known collectively as Parinauds syndrome or Dorsal Mid-brain syndrome, are the only physical symptoms seen. This is caused by the compression of the vertical gaze center in the midbrain tectum at the level of the superior colliculus and cranial nerve III. Work-up usually includes Neuro-imaging as seen on the right.A pinealoma may cause interruption of hypothalamic inhibiting pathways, sometimes leading to beta-hCG secretion and consequent Leydigs cell stimulation (endocrine syndrome).Other symptoms may include hydrocephalus, gait disturbances, and precocious puberty. Cause
Pinealomas can be due to proliferation of primary pineocytes (pineocytomas, pineoblastomas), astrocytes (astrocytoma), or germ cells (germinoma). Germinomas are the most common tumor in the pineal gland. Diagnosis
Treatment
Prognosis
Of the different types of pinealomas, the type with the most favorable prognosis is the pineocytoma. References
External links
00322 at CHORUS