Snapshot A 26-year-old male presents with bilateral gradual hearing loss mostly of his left ear. He reports having difficulty hearing conversations when the phone is on his left side. Family history is significant for neurological disease in his father, but he cannot recall the name. He does state that his father complains of headaches and has to be followed every 3-5 years with an MRI of his brain and spine. Weber and Rinne testing suggest a sensorineural hearing loss mostly affective the left ear. Skin examination is shown on the right. Introduction Glial cells play a supportive role for neurons outnumber the amount of neurons in the central nervous system (CNS) Glial cells can be divided into macroglia and microglia macroglia three main types: oligodendrocytes, astrocytes, Schwann cells microglia cells of the immune system for the CNS Neuroglial Cells Neuroglial Cells Glial Cell (and Its Origin) Function Clinical Correlate Astrocytes (neuroectoderm) GFAP (+) Foot processes envelope neurons and capillaries mantain blood-brain barrier Involved in neurotransmitter metabolism (e.g.,GABA, glutamate) Uptake excess K+ in the extracellular space, acting as aK+ buffer thus maintain neuronal signaling efficiency Neuronal injury → reactive gliosis (glial scar) Contain glycogen granules can provide glucose to neurons Glioblastoma multiforme (grade IV astrocytoma) primary brain tumor that is highly malignant ability to cross the corpus callosum→ "butterfly glioma" pseudopalisades on histology associated with necrosis Oligodendrocytes (neuroectoderm) Myelinates neurons in the CNS ~30 CNS axons ↑ speed of conduction via saltatory conduction Fried egg-appearance on histology Oligodendroglioma classic histology findings of"fried egg" appearance with "chicken wire loop" capillaries Multiple sclerosis loss of oligodendrocytes can be histologically seen in white matter plaques Progressive Multifocal Leukoencephalopathy (PML) secondary to reactivation of JC virus infection in the immunocompromised→ lytic damage to oligodendrocytes Microglia (mesoderm) CNS scavenger cells phagocytic cell that has the ability to present antigens to lymphocytes tissue damage (e.g.,stroke, neurodegeneration, infection) leads to its activation Microglia infected with HIV→ multinucleated giant cells in CNS Ependymal cells (neuroectoderm) Cililated cells that line the central canal and ventricles of the CNS aids in moving cerebrospinal fluid (CSF) throughout the ventricular system At certain places in the CNS, the ependymal cells are continuous with the choroid plexus leads to CSF production Ependymoma commonly found in 4th ventricle risk of leading to hydrocephalus perivascular rosettes on histology Schwann cells(neural crest) Myelinates axons in the peripheral nervous system (PNS) Each cell myelinates 1 PNS axon ↑ speed of conduction via saltatory conduction Involved in nerve regeneration Can act as phagocytes to remove debri post neuronal damage Guillain-Barré syndrome (GBS) respiratory or gastrointestinal illness→ acute inflammatory reaction to peripheral nerves (may affect Schwann cells) e.g.,Campylobacter jejuni (classic), Mycoplasma pneumoniae acute inflammatory demyelinating polyradiculopathy (most common subtype of GBS) Vestibular schwannoma (acoustic neuroma) commonly affects vestibular portion of cranial nerve VIII can expand to the cerebellopontine angle after it fills the internal auditory meatus bilateral acoustic neuroma is a characteristic feature of neurofibromatosis type 2 (NF2) mutation in merlin protein on chromosome 22