Nerve Sheath Tumor in Dogs

Schwannoma in Dogs

Schwannomas are tumors that originate in the myelin sheath. The myelin sheath is produced by the Schwann cell, a specialized cell which surrounds the peripheral nerves, providing mechanical and physical support for the nerves as well as insulating the nerves that transmit the nervous system’s electrical signals. The peripheral nervous system consists of the nerves outside of the central nervous system (brain and spine). Peripheral nerve sheath tumor is the term that has been proposed to include schwannomas, neurofibromas (nerve fiber tumors), neurofibrosarcomas (malignant nerve fiber tumors), and hemangiopericytoma (tumor of blood vessels and soft tissue), since they are all believed to arise from the same cell type.

Symptoms and Types

  • Chronic, progressive forelimb lameness and muscle atrophy
  • Lameness in the hind limbs
  • Peripheral nerve disorder (from self-mutilation)
  • Palpable mass (mass can be felt by touch examination)
  • Horner’s syndrome, a disease of the sympathetic nervous system: automatic nerve reaction, affects parts of the body not under direct control
  • If the Schwannoma is in the neck, only one side of the face will be affected:
    • Droopy eyelid
    • One sided facial paralysis
    • Decreased pupil size
    • Slight elevation of the lower eyelid

 

Causes

  • Idiopathic (unknown)

 

Diagnosis

Your veterinarian will perform a complete physical exam on your dog, including a blood chemical profile, a complete blood count, a urinalysis and an electrolyte panel. You will need to provide a thorough history of your dog’s health leading up to the onset of symptoms. A computed tomography (CT) or, ideally, a magnetic resonance imaging (MRI) can provide the most information regarding the extent and location of the disease. An electromyogram (a measurement of muscle activity) will show abnormal muscle activity if there is a schwannoma present.

nerve

A bundle of fibers that are used in the process of sending impulses through the body

peripheral nervous system

That part of the nervous system that includes the cranial nerves and spinal nerves

urinalysis

An in-depth examination of the properties of urine; used to determine the presence or absence of illness

myelin

A type of covering over certain nerve cells; may be found in areas of the spinal cord or on the brain’s white matter

sympathetic nervous system

The part of the nervous system that allows the body to react to a stressful situation

lymph nodes

Small structures that filter out the lymph and store lymphocytes

electromyogram

A record of the strength of contractions of the muscles that are caused by electrical stimulation

lameness

Any type of pain or tenderness or lack of soundness in the feet or legs of animals

laminectomy

The removal of the lamina as a method of relieving pain and pressure on the spine

atrophy

The wasting away of certain tissues; a medical condition that occurs when tissues fail to grow.

malignant

Something that becomes worse or life threatening as it spreads

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