neuroscience pathophysiology of the nervous system dr. michael p. gillespie

NeurosciencePathophysiology of the Nervous SystemD

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Abnormalities in Development of the Nervous System

Spina Bifida

Syringo(hydro)myelia

Tethered cord

Encephalocele

Dandy-Walker Syndrome

Anencephaly

Dr. Michael P. Gillespie2

Spina Bifida

Spina bifida is Latin for “split spine”.

It is a developmental congenital disorder.

Spina Bifida is called myeloschisis.

It is caused by incomplete closing of the neural tube.

Some vertebra, not fully formed, remain unfused and open.

This can allow a portion of the spinal cord to protrude through the opening in the bones.

The lumbar and sacral areas are most commonly affected.

Spina bifida can be surgically closed after birth, but this does not restore normal function to the affected portion of the spinal cord.

Spina bifida is decreased by up to 70% when the mother takes daily folic acid supplements.


Categories of Spina Bifida

Spina bifida occulta

Spina bifida cystica with meningocele

Spina bifida cystica with myelomeningocele Most significant and most common form


Spina Bifida


Spina Bifida Occulta

Occulta is Latin for “hidden”.

This is the mildest form of spina bifida.

The posterior portion of the vertebra is not completely closed.

The splits are so small that the spinal cord does not protrude.

The skin at the site of the lesion may be normal, it may have some hair growing from it, there may be a dimple in the skin, or there may be a birthmark.

Approximately 10% of the population have spina bifida occulta.

It is asymptomatic in most cases and most people are diagnosed incidentally from x-rays.


Spina Bifida Occulta


Meningocele

This is the least common form of spina bifida.

In this form, the vertabrae develop normally, but the meninges are forced into the gaps between the vertebrae.

The nervous system is undamaged with this kind of spina bifida so these individuals are unlikely to suffer long-term health consequences.


Myelomenigocele

This is the most severe form of spina bifida.

The unfused portion of the spinal column allows the spinal cord to protrude through the opening.

The meningeal membranes that cover the spinal cord form a sac that encloses the spinal cord structures.

The area involved is represented by a flattened, plate-like mass of nervous tissue with no overlying membrane.

The baby is more susceptible to infections such as meningitis due to the lack of protection.


Myelomenigocele

1. External sac with cerebrospinal fluid.

2. Spinal cord wedged between the vertebrae.


Signs and Symptoms of Spina Bifida

Physical complications Leg weakness and paralysis Orthopedic abnormalities Bladder and bowel control problems (incontinence,

UTI) Pressure sores and irritations Abnormal Eye Movement 68% of children with spina bifida have an allergy to

latex The spinal cord lesion or the scaring from surgical

correction can result in a tethered spinal cord.



Neurological complications Arnold Chiari malformation – an associated abnormality.

The back portion of the brain is displaced from the back of the skull into the upper neck.

The cerebellar tonsils displace downward through the foramen magnum.

Hydrocephalus – the displaced cerebrum interferes with the flow of cerebrospinal fluid.

Corpus callosum mal-development – affects communication between the right and left hemispheres.

White matter tracts are less organized Cortex abnormalities – frontal regions tend to be

thicker, parietal regions tend to be thinner


Arnold Chiari Malformation



Executive function Difficulty with planning, organizing, initiating, and

working memory. Difficulty with problem solving, abstraction, and

visual planning. Poor cognitive flexibility. Higher rates of ADHD.

Academic skills Individuals with spina bifida may struggle

academically, especially in the subjects of mathematics and reading.



Social complications May have fewer friends than their peers May spend less time with their peers May be more socially immature May be more passive in social situations Have reported feeling less close to their friends



A cyst or cavity filled with CSF forms within the spinal cord in the region of the central canal.

It can expand and put pressure on the cord, ultimately destroying regions of the cord.

It often affects the spinothalamic tract causing segmental loss of pain and temperature.

It often affects the corticospinal tract causing loss of motor function.

Tactile sensation is typically spared.


Tethered Spinal Cord

The spinal cord lesion or the scaring from surgical correction can result in a tethered spinal cord.

A tethered cord causes the spinal cord to stretch as the child grows.

It is often associated with the closure of a spina bifida.

Signs and symptoms:

Lesions, hairy patches, dimples, or fatty tumors on the lower back

Foot and spinal deformities

Weakness in the legs, low back pain, scoliosis, incontinence


Encephalocele

Sometimes known by the Latin name cranium bifidum.

A protrusion of a sac from the cranium consisting of portions of the meninges, CSF, glial tissue and brain substance.

Mental retardation and corticospinal tract dysfunction are common.

Seizures are often present.


Encephalocele


Detecting Neural Tube Defects

Ultrasound examination

Amniocentesis

Alpha-fetoprotein leaks out into the amniotic fluid when the neural tube fails to close, which results in significantly elevated levels of this protein.



A congenital brain malformation involving the cerebellum and the fluid filled chambers around it.

Absence of the lateral apertures (of Luschka) and the median aperture (of Magendie).

Lack of communication between the ventricular system can cause hydrocephalus.

Signs and symptoms Slower motor development and progressive enlargement of

the skull. Increased intracranial pressure leads to irritability, vomiting,

convulsions, unsteadiness, lack of coordination, jerky movements of the eyes, abnormal breathing patterns.

Increased head circumference, bulging at the back of the skull.


Anencephaly

A neural tube defect in which the rostral head fails to close resulting in an absence of a major portion of the brain, skull, and scalp.

Most babies with this disorder do not survive.


Anencephaly


Disorders Associated with the Meninges

Meningitis

Meningiomas

Epidural hematoma

Subdural hematoma

Subarachnoid hemorrhage


Meningitis

Infection of the meninges.

Most commonly caused by bacterial, viral, or fungal infection.

Bacterial meningitis is the most serious and needs prompt treatment.

Most commonly caused by Streptococcus penumoniae and Neisseria meningitidis.

Symptoms develop rapidly (within 24 hours) and may last for days. In subacute meningitis, the onset of symptoms is slow and the course of the disease is longer (weeks).


Meningitis Signs and Symptoms

Headache

Fever

Chills

Stiff neck

Vomiting

Photophobia (fear of bright lights)

Confusion

Approximately 1/3 suffer from seizures.


Meningitis


Meningiomas

A tumor arising from the meninges.

Generally slow growing.

They can be benign (typical), atypical, or malignant.

Benign consist of slow growing cells, atypical consist of fast growing cells, malignant consist of aggressively growing cells.

Treatment consists of surgical removal or radiosurgery (external beam of radiation aimed at the tumor).


Meningiomas


Epidural Hematoma

Head injury can result in the loosening of the periosteal dura from the cranium.

The middle meningeal artery may be damaged leading to extravasation of blood.

An extradural hematoma can cause headaches, disorientation, and lethargy.


Subdural Hematoma

Normally, there is no space between the dura and subarachnoid mater.

Veins pass through the subarachnoid space to reach the dural sinuses.

Head injury can damage these veins leading to extravasation of blood and form a subdural hematoma.

This can increase intracranial pressure and therefore damage the brain tissue.


Subdural Hematoma


Subarachnoid Hemorrhage

Bleeding into the subarachnoid space.

This can be caused by rupture of a cerebral aneurysm (tend to be in the circle of willis) or result from head injury.

Subarachnoid hemorrhage is associated with intense headache, nausea and vomiting. It ultimately results in unconsciousness.


Subarachnoid Hemorrhage Signs & Symptoms

Thunderclap headache – a headache described as “like being kicked in the head” or “the worst ever”.

The headache develops within seconds to minutes.

The headache pulsates towards the occiput.

Vomiting may be present.

1 in 14 have seizures.

Confusion, decreased level of consciousness, or coma may be present.

Increased intracranial pressure, which can lead to intraocular bleeding.


Disorders of the Cerebrospinal Fluid System

Hydrocephalus

Increase in intracranial pressure


Hydrocephalus

Hydrocephalus (dilation of the ventricles) occurs when there is blockage of CSF circulation or absorption is impaired.

This increases ventricular pressure causing ventricular dilation.

Ventricular dilation exerts pressure on adjacent tissue such as the corticobulbar and corticospinal tracts.

This impairs motor function.


Hydrocephalus


Increase in Intracranial Pressure

An increase in the size or volume of any component of the cranial cavity results in an increase in intracranial pressure.

Causes Cerebral edema Intracerebral hemorrhage Tumor Obstruction of CSF Obstruction of venous blood flow

Symptoms Headache, nausea, vomiting, bradycardia, increase in

systemic blood pressure, loss of consciousness, blurring of the optic disc.


Disorders Affecting the Conduction of Action Potentials

Lambert-Eaton Syndrome

Gullian-Barre Syndrome

Prion Diseases

Cystic Fibrosis



A rare autoimmune disorder.

Often associated with small-cell carcinoma of the lung.

Antibodies are formed against presynaptic voltage-gated calcium channels at the neuromuscular junction.

Characterized by muscle weakness in the limbs.

The proximal muscles are typically affected. This causes difficulty in climbing stairs and rising from the seated position.

¾ of the people also have disruption of the autonomic nervous system. Dry mouth, constipation, blurred vision, impaired sweating,

orthostatic hypotension, metallic taste in the mouth.


Gullian-Barre Syndrome

An acute polyneuropathy affecting the peripheral nervous system.

Symmetrical weakness that usually affects the lower limbs first.

Patients notice weakness in their legs (“rubbery legs” or legs that tend to buckle).

Ascending paralysis (beginning in the feet and hands and migrating towards the trunk).

It can cause life threatening complications particularly if the muscles of respiration are affected.

It is an autoimmune disease that is usually triggered by an infection.

Most patients will completely recover.


Multiple Sclerosis

The cause of multiple sclerosis (MS) is unknown.

It may be autoimmune.

Antibodies develop against the myelin sheath in the CNS.

Demyelination occurs

The myelin swells and detaches

A scar (sclerosis) occurs

Nerve fibers degenerate

MS affects young people, especially women (20-40)


Multiple Sclerosis


Prion Diseases

A prion is an infectious agent consisting primarily of a protein.

Creutzfeldt-Jakob Disease, Kuru, and bovine spongiform encephalopathy (mad cow disease) are caused by infectious prions.

Dementia occurs with myoclonic jerks.

Transmission results from consumption of infected central nervous system tissue.


Mad Cow Disease


Lesions of the Spinal Cord

Spinal cord transection

Brown-Sequard Syndrome

Amyotrophic Lateral Sclerosis (Lou Gehrig’s Disease)

Syringomyelia

Lesions of the Dorsal Root

Lesions of the Ventral Root


Spinal Cord Transection

A complete transection of the spinal cord results in loss of muscle tone, motor function, reflex activity, visceral sensation, and somatic sensation below the level of the transection.



Brown-Sequard Syndrome involves a hemisection (cutting) of the spinal cord.

It is a spinal cord injury that is an incomplete lesion.

Loss of motor function (hemiparaplegia), loss of vibration sense and fine touch, loss of proprioception, loss of two point discrimination, and signs of weakness on the ipsilateral side of the spinal injury.

Loss of pain, temperature, and crude touch on the contralteral side of the lesion 2 segments below the lesion.


Amyotrophic Lateral Sclerosis (Lou Gehrig’s Disease) (ALS)

Amyotrophic Lateral Sclerosis (Lou Gehrig’s Disease) is characterized by rapidly progressing weakness, ,muscle atrophy, fasciculation, muscle spasticity, difficulty speaking (dysarthria), difficulty swallowing (dysphagia) and difficulty breathing (dyspnea).

Head trauma, military service, contact sports can all be causal factors.

It most commonly strikes people between 40 and 60 years of age.


Lesions of the Dorsal Root

Section of three consecutive dorsal roots causes abolition of all sensory function in a particular dermatome.

Section of one dorsal root does not eliminate sensory function because of overlap between dermatomes with adjacent dorsal roots.


Lesions of the Ventral Root

These lesions abolish motor functions of the affected segment.


Cystic Fibrosis

Cystic fibrosis is an autosomal recessive genetic disorder.

It affects primarily the respiratory system.

It also affects the pancreas, liver, and intestines.

Mutation affects the ability to make the protein cystic fibrosis transmembrane protein.

Tissues that produce mucus, sweat, saliva, tears, and digestive enzymes use this protein.

Mucus is thicker than normal and leads to obstruction of the respiratory tract. This leads to repeated respiratory infections.


Cystic Fibrosis Signs & Symptoms

Salty tasting skin

Poor growth and poor weight gain despite normal food intake

Accumulation of thick, sticky mucus

Frequent chest infections, coughing, and shortness of breath

Clubbing of the fingers and toes


Cystic Fibrosis Clubbing


Cystic Fibrosis


Upper Motor Neuron Syndrome

Upper motor neuron syndrome consists of the motor changes that occur in skeletal muscles following an upper motor neuron lesion.

An upper motor neuron lesions is a lesion of the neural pathway above the anterior horn cell of the spinal cord or above the motor nuclei of the cranial nerves.

Conditions affecting motor neurons in the brain and spinal cord such as stroke, multiple sclerosis, traumatic brain injury and cerebral palsy can cause an upper motor neuron lesion.


Upper Motor Neuron Syndrome Symptoms

Muscle weakness

Decreased control of active movement (slowness)

Spasticity

Clasp-knife response – initial higher resistance to movement is followed by lesser resistance

Babinski skign is present

Increase in deep tendon reflex

Pronator drift


Cerebellar Disorders

Ataxia

Hypotonia

Cerebellar Nystagmus and Gait Ataxia

Syndromes Associated with the midline region of the Cerebellar Cortex

Syndromes Associated with the Cerebellar Hemispheres


Ataxia

Ataxia is a neurological sign consisting of lack of voluntary coordination of muscle movements.

Damage to to cerebellum can result in ataxia.

It can affect the force, range, direction, and velocity of movement.

Decomposition of movement – complex movements occur as a series of simply individual movements.

Dysmetria – the patient will undershoot or overshoot his mark.

Intention tremors may be present.


Hypotonia

Hypotonia is a state of low muscle tone and often reduced muscle strength.

It is associated with damage to the cerebellar cortex; however, the precise mechanism underlying the disorder is unknown.


Disorders of the Autonomic Nervous System

Orthostatic Hypotension

Horner’s Syndrome

Argyll Robertson Pupil

Hirschprung’s Disease (Megacolon)

Raynaud’s Syndrome


Orthostatic Hypotension

Also known as postural hypotension.

The blood pressure suddenly falls when standing up or stretching.

It is caused by blood pooling in the lower extremities.

It can occur in anyone, although it is quite common in the elderly and those with low blood pressure.

Dizziness, lightheadedness, nausea, headache, blurred vision, distortions in hearing can all occur.


Horner’s Syndrome

Horner’s Syndrome is the combination of ptosis (drooping of the eyelid), miosis (constriction of the pupil, anhidrosis (decreased sweating) on one side of the face due to disruption of the sympathetic division of the ANS.

It sometimes has a congenital cause; however, it could reflect a pancoast tumor.


Argyll Robertson Pupil

Argyll Robertson pupils are bilateral small pupils that constrict when the patient focuses on a near object, but do not constrict when exposed to bright light.

They accommodate, but do not react to light.

It is usually associated with a benign peripheral neuropathy.

Late stage syphilis can cause the condition.


Hirschsprung’s Disease (Megacolon)

Hirschsprung’s disease is a disorder in which all or part of the large intestine has no nerves and therefore cannot function.

It is a congenital disorder in which Auerbach’s plexus does not form.

The affected segment of the colon cannot relax, which blocks the passage of stool.


Raynaud’s Disease

Raynaud’s phenomenon or disease is a vasospastic disorder causing discoloration of the fingers, toes and occasionally other areas.

The nails may become brittle.

Vasospasm decreases blood supply to the affected regions.

In the disease the cause is considered to be idiopathic. In the phenomenon it is secondary to another condition such as lupus.


Raynaud’s Disease


Common Peripheral Nerve Entrapments

Upper Extremity Axillary Nerve Long Thoracic Nerve Median Nerve Ulnar Nerve Radial Nerve

Lower Extremity

Sciatic

Femoral


neuroscience pathophysiology of the nervous system dr. michael p. gillespie

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