Diseases of the Horse Nervous System

Some Common Nervous System Diseases

• Apoplexy or Cerebral Hemorrhage: Apoplexy is often confused with cerebral congestion, but true apoplexy always consists in rupture of cerebral blood vessels. Two causes are involved in the production of apoplexy, the predisposing and the exciting. The predisposing cause is degeneration, or disease which weakens the blood vessel; the exciting cause is any one which tends to induce cerebral congestion.
  
  
• Congestion of the Brain: Congestion of the brain consists in an accumulation of blood in the vessels, also called hyperemia, or engorgement. It may be active or passive—active when there is an undue accumulation of blood or diminished arterial resistance and passive when it accumulates in the vessels of the brain, owing to some obstacle to its return by the veins.
  
  Extremely fat animals with short, thick necks are peculiarly subject to attacks of cerebral congestion. Simple congestion, however, is merely a functional affection, and in a slight or moderate degree involves no immediate danger. Extreme engorgement, on the contrary, may be followed by rupture of previously weakened arteries and capillaries and cause immediate death, designated then as a stroke of apoplexy.
  
  
• Epilepsy: The cause of epilepsy is seldom traceable to any special brain lesions or nervous system disease. In a few cases it accompanies disease of the pituitary body, which is located in the under surface of the brain. Softening of the brain may give rise to this affection. Attacks may occur only once or twice a year or they may be of frequent recurrence.
  
  
• Inflammation of the Brain and its Membranes: Inflammation may attack these membranes singly, or it may invade the whole at once. When inflammation invades the brain and its enveloping membranes it is properly called encephalitis; when the membranes alone are affected it is called meningitis, or the brain substance alone, cerebritis. These nervous system diseases merge into one another and can scarcely be recognized separately during the life of the animal.
  
  These horse diseases can be caused by exposure to extreme heat or cold, sudden and extreme changes of temperature, excessive continued cerebral excitement, too much nitrogenous feed, direct injuries to the brain, such as concussion, or from fracture of the cranium.
  
  Usually the first symptoms indicate mental excitement and are followed by symptoms indicating depression. Acute encephalitis may be ushered in by an increased sensibility to noises, with more or less nervous excitability, contraction of the pupils of the eyes and a quick, hard pulse. This condition will soon be followed by muscular twitching, convulsive or spasmodic movements, eyes wide open with shortness of sight.
  
  The symptoms may follow one another in rapid succession, and the disease may approach a fatal termination within 12 hours. In sub-acute attacks the symptoms are better defined, and the animal seldom dies before the third day. Within three or four days gradual improvement may become manifest. In all cases of encephalitis there is a marked rise in temperature from the very onset of the disease
  
  
• Tetanus: This nervous system disease of the horse is characterized by spasms affecting the muscles of the face, neck, body and limbs and of all muscles supplied by the cerebrospinal nerves. The spasms or muscular contractions are rigid and persistent, yet mixed with occasional more intense contractions of convulsive violence.
  
  This disease is caused by a bacillus that is often found in the soil, in manure and in dust. This germ forms spores at the end of the organism and grows only in the absence of oxygen. It produces a powerful nerve poison, which causes the symptoms of tetanus.
  
  In an acute attack the animal usually dies within four days. The first symptoms which attract the attention of the owner are difficulty in chewing and swallowing. An examination of the mouth will reveal an inability to open the jaws to their full extent.
  
  
• Tumors within the Cranium:Tumors within the cranial cavity and the brain occur not infrequently and give rise to a variety of symptoms, such as imperfect control of voluntary movement, local paralysis and epilepsy. Treatment for tumors of the brain is impossible.

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