Head and Central Nervous System Anomalies

Head and central nervous system anomalies include microcephalus, cyclopia, hydrocephalus, meningocele, facial fissures, lack of cranial, cerebellar hypoplasia, hydranencephaly and arthrogryposis, and crooked calf disease in animals.

Anomalies of Central Nervous System

Central nervous system anomalies are:

1. Microcephalus
2. Cyclopia or Cebocephalus
3. Hydrocephalus
4. Meningeocele

1. Microcephalus

Microcephalus is characterized by a small cranial cavity and brain.

2. Cyclopia

Cyclopia or cebocephalus is seen most commonly in the pig and, sheep but may be present in all species. single orbit in which global tissue is absent or rudimentary or in which the eye balls vary from a single apparently normal eye thorough all degrees of doubling to one consisting of two complete but small adjacent globes. Eyelids are rudimentary or absent and the noses usually absent or in the form of tubular appendages placed above the centrally located eye. The rudimentary nose does not communicate with the pharynx the skull is usually small and the lower jaw being longer than the defective upper jaw is curved dorsally at its cranial end.

3. Hydrocephalus

Hydrocephalus occurs due to an abnormal accumulation of fluid in the cranial cavity. Internal hydrocephalus is due to excessive fluid in the ventricular system. External hydrocephalus is rare and due to excessive fluid between the brain and dura mater. Internal and external hydrocephalus may be combined. In marked cases, the dorsal portion of the brain is encompassed only by the skin, the subcutaneous tissues, and the brain coverings.

4. Meningocele

Meningocele or cranioschisis or crania bifida are the defects of the skull that may result in meningoencephalocele or meningocele . In the later instance the skull defect is large, so that parts of the brain and the meninges are extruded.

Anomalies of Head

Anomalies of head are:

1. Facial fissures
2. Lack of cranial or facial structures
3. Cerebellar hypoplasia and allied defects
4. Hydranencephaly and arthrogryposis or muscle contractures
5. Crooked calf disease

1. Facial Fissures

Palatoschisis, cheiloschisis, macrostomia, and schistoprosopus or divided face are the facial fissures of the head.

2. Lack of Cranial or Facial Structures

Acephalia, or absence of a head; acrania; hemicrania; astomia; microstomia, arhinencephalia or absence of a nose, agnathis, hypognathia, anophthalmus, microphthalmia, aprosopia or partial or complete absence of a face, anotia or absence of ears, polyotia and polydontia or anodontia.

Congenital defects of the head and ears of ovine fetuses are common. Anophthalmus and microphthalmia may possibly be related to a severe vitamin A deficiency.

3. Cerebellar Hypoplasia and Allied Defects

Possible genetic or congenital abnormality in all domestic animals. Cerebellar hypoplasia or aplasia can be produced in newborn kittens by infecting the pregnant dam with feline panleucopenia virus.

It can be produced in newborn calves by infecting the pregnant dam around the fifth month of gestation with BVD-MD virus.

4. Hydranencephaly and Arthrogryposis or Muscle Contractures

Hydranencephaly and arthrogryposis or muscle contractures in newborn calves of various breeds. Blindness was also a part of this syndrome in some calves.

The agent causing the anomalies was believed to have been active between 2 and 6 months of gestation.

5. Crooked Calf Disease

Crooked calf disease characterized by arthrogryposis, torticollis, scoliosis and occasionally cleft palate.

These anomalies of the central nervous system are often characterized externally by ankylosed joints, deformed fetlocks or “club feet” and other defects including- hydramnios in some severely affected fetuses. As with other markedly defective fetuses their size is usually smaller than normal.