Transcript 流行脑脊髓膜炎 Epidemic cerebrospinal meningitis

Chapter 14
Diseases of the Nervous System
南通大学基础医学院
Chen li
The specificness of diseases of the nervous system:
1
The localization of function in the CNS, which has four major consequences:
(1) The brain is vulnerable to small focal lesions that would be
asymptomatic in other organs.
(2) The same pathologic process manifests in a different way when it
affects a different part of the system ，e.g. meningioma :in the
factory groove ---anosmia ， at the foramen magnum ---progressive
quadriparesis.
(3) There are regions of selective vulnerability to particular pathologic
insults, e.g., Purkinje cells of the cerebellum and pyramidal neurons
of the hippocampus are particularly vulnerable to ischemia.
(4) The same type of pathologic change can occur in different diseases
(e.g., neurofibrillary tangles). Diagonosis is by distribution
(localization) of the pathologic change.
2
The nervous system has specific anatomic and physiologic features that affect the
expression of disease, principally the presence of the skull, the CSF, the blood-brain
barrier, and the absence of lymphatic drainage.
3 Diseases of the nervous system fall into two main groups:
(1) Those that occur in both the nervous system and other organs , e.g.,
ininfections.
(2) Conditions unique to the nervous system, notably the diseases of myelin
and system degenerations of neurons.
Section 1 Infectious diseases
① those of the meninges and CSF ------meningitis
②those of the brain parenchyma ------encephalitis
③meningitis extends into the brain or encephalitis spills
over into the CSF-----Meningoencephalitis
Bacterial infection-----Epidemic cerebrospinal
meningitis
Viral infection------Epidemic encephalitis B
------ Poliomyelitis
------Spongiform Encephalopathies
一、Epidemic cerebrospinal meningitis
It is an acute purulent inflammation of meninges
which was caused by meningococcus .
Epidemic cerebrospinal meningitis is the most
frequent pyogenic infection of the nervous system. It
may occur at any age but is most common in children.
（一）Etiology and pathogenesis
Etiology
The most cause was :meningococci, pneumococci, streptococ
and hemophilus.
The second was：Staphylococci and gram-negative bacteria
Pathogenesis
microorganisms
infected sinus
meninges
or ear
septicemia
2%-3%
breakthrough the blood brain barrier
meningitis
Meningina
;arachnoid
（二）Clinical features （exclude fever and other
systemic infection symptoms）
The main symptom of nervous system：
1、increased intracranial pressure （inflammation、hydropsia):
intense headache, projectile vomiting,infant bregmatic space
projectile
2、the symptom of meningismus：
stiffneck defend spasmus and limitation of movement
infant opisthotonus
positive of kernig
3、the symptom response to cranial nerve palsy（Ⅲ、Ⅳ、Ⅴ、 Ⅵ、Ⅶ pair)
4、the variation of CSF ：cloudy 、increased pressure、as many as 90,000
neutrophils/mm3 , a raised protein level, a reduced glucose content, bacteria may be
seen on a smear .
（三）Pathology
Grossly
A varying amount of
exudates is seen in the
subarachnoid
space
overlying the base of
the brain and spinal
cord.
Exudates distribute
along the blood vessel,
yellow.The structer of
cortical sulci and cerebral
convolution are not clear.
Microscopical
1、 The subarachnoid space contains pus(many pus cells+Lc
and Mc+diplococcus）
2、The exudates confined to the leptomeninges. The underlying
brain and cord are edematous and congested.
3、In fulminant meningitis, inflammatory cells infiltrate and
produce a venulitis that may lead to venous occlusions and
infarctions.
（四）Prognosis
Recovery with complete resolution is common motality is
less than 5% to 10%.
（五）Complications
If a low-grade infection persists, trabeculae form across the
subarachnoid space, follow by progressive fibrosis, with
narrowing or localized obliteration of the subarachnoid
space.
When such changes are localized to basilar leptomeninges
near the foramina, the outflow of CSF from the ventricular
system is blocked, leading to hydrocephalus.
The symptoms response to cranial nerve palsy ：Permanent
disabilities include facial paralysis, deafness, strabilismus,
speech defect,or mental deficiency.
Fulminant Neisseria intracellularis septicemia（addition）
It is a type of fulminant cerebrospinal meningitis .And it most common in
children.
The onset is usually sudden. Patient's condition is dangerous,and often die in
short term.
Clinical feature
peripheral circulatory failure
shock
skin Purpura
Pathology
Waterhouse-Friederichsen syndrome
pathological changes of meninges is light
Waterhouse-Friederichsen syndrome fingers two sides adrenal gland severity
bleeding in severity septemia ,and adrenal cortex nonfuction.It often occurs in
fulminant Neisseria intracellularis septicemia
Pathogenesis releasing of endotoxin induce toxic shock and DIC.
Fulminant meningocerebritis
Pathology
meningitis
brain tissue beneath meningina:
brain tissue congestion
Severity brain edema
Clinical
sudden increase of intracranial pressure
outbreak ardent fever
severe headache
frequent vomitus
eclampsia、coma or cerebral hernia
二、Viral infections
（一）Pathogenesis
When infection of the brain parenchyma is termed,
encephalitis and viruses involve the CNS, they invade both
neural and meningeal areas, producing a
meningoencephalitis
route of transmission：
via an insect bite （equine encephalitis ），
by the gastrointestinal route (poliomyelitis) ，
via the skin or mucosa (herpes) ，
it may reach the CNS via the peripheral nerves （rabies）
or by hematogenous spread.
（二）Pathology
1
neuron degeneration
gliosis ；
perivascular inflammatory response (chiefy in
mononuclear cells ) .
2 Inclusion bodies are seen in neural and glial cells in some
infections
These bodies may be nuclear (herpes) or cytoplasmic(rabies).
The characteristic Negri bodies seen in rabies are eosinophilic, oval
to bullet-shaped, intracytoplasmic inclusions found only in neurons.
Viral tropism is particularly striking in the nervous
system; e.g., poliomyelitis affects anterior horn motor
neurons.
Latency is also important, particularly with herpes
simplex and varicellazoster. Slow virus diseases have both
a long latent period and a slow progression.
3 Other virus-associated effects :
(1) An immune-mediated perivenous encephalitis;
(2) Reye’s syndrome;
(3) Congenital malformations;
(4) Post encephalitis Parkinson’s disease(post viral
influenza).
（三） Major tpyes
1、Epidemic encephalitis B
2、Poliomyelitis
3、Spongiform Encephalopathies
1、Epidemic encephalitis B
（一）Etiology
Etiology infection of arthropod-borne viruses . Most cases of
arbovirus encephalitides occur in late summer.
Vectors
mosquitoes
long-term long-term long-term(cow,horse,pig)
Infection sources silent infection of patients , cow,horse and pig
（二）Morphology
Grossly ：
Brain Substance swelling、
congestion 、edema
microscopically ：
(1) Nonspecific perivascular inflammation
,(perivascular cuffing)
(2) Glialcell proliferation become microglial
nodules, which are sometimes most
pronounced in the brain stem are seen.
(3) Neuron degeneration necrosis ：
Satellitosis
neuronophagia
Focal parenchymal soften with
necrosis inflammatory cells
infiltration.
① Satellitosis :
neuron undergo degeneration and
surround at least five proliferative
oligodendroglial cells,which from
satellitoid structure.
② neuronophagia:
the process is that neuron
is phagacyted by
proliferative small glial
cells or macrophages.
③ form of focal parenchymal soften
Definition focal necrosis and liquation of nervous tissues,which
formed puff texture、dilute stain grit focus of infection.
（三）Clinical features
1、seizures, confusion or coma:the most early and main
symptoms
2、sometimes with headache, vomit intracranial hypertension
and herniation,
Cerebellar tonsillar hernia can cause
sudden breathing stop and
death by press the
medullary respiratory center.
2、 Poliomyelitis
Etiology ： Poliomyelitis is caused by poliovirus, a small
RNA virus that is transmitted gastrointestinally by sewagecontaminated water. The virus is neurotropic, chiefly
affecting the spinal cord and brain stem.
Clinical features ： Patients may or may not manifest
gastrointestinally symptoms; but within a few weeks of
infection, they show lower motor neuron paralysis, usually
affect the lower limbs. The brain stem neurons may
become affected, and the resultant respiratory paralysis
may be fatal. Surviving patients have significant neurologic
sequelae, especially affecting the legs.
Clinically, loss of lower motor neurons produces a
permanent flaccid paralysis with muscle wasting and
hyporeflexia in the affected spinal segments.
Pathology
Grossly ： the spinal cord may show small hemorrhages and congestio
Microscopically The anterior horn cells of the cord are affected
predominantly
neutrophilic infiltration
gliosis
marrow intumescentia
lumbalis is
predominantly.
more up more lessen
atrophy of the anterior
(motor) spinal roots,
and neurogenic
atrophy of the
denervated muscle.
3、 Spongiform Encephalopathies
The spongiform encephalopathies represent a group of diseases that includes
Creutzfeldt-Jacob disease(CJD) and a number of other exceedingly rare
conditions(kuru; Gerstomann-Straussler syndrome and fatal familial insomnia;
and, in some animals, scrapie and “mad cow” disease). These diseases are
transmitted by a unique category of proteinaceous infectious particles termed
prions that lack DNA or RNA. Infectious prions are a modified form of a
normal structural protein found in the mammalian nervous system. The major
difference between normal prion proteins and pathogenic prions is in their
conformation. Apparently, the pathogenic prions propagate themselves by
contacting their normal counterparts and inducing them to refold in the
pathogenic conformations. As this cycle continues, an ever-increasing
population of normal prion proteins is converted into the disease-causing
form.
Because they lack nucleic acids, prions are remarkably resistant to many
agents that normally inactivate viruses, such as ultraviolet light and standard
disinfectants.
CJD is probably the best characterized of the human
spongiform encephalopathies. Both sporadic and familial cases of
CJD occur, and rare instances of iatrogenic transmission have
occurred in patients who have received corneal transplants and
human pituitary extract. In the early stages of CJD, the brain is
grossly normal. Atrophy is present in cases of long duration and
may be severe. The hallmark of CJD and other spongiform
encephalopathies is the presence of vacuoles within neuropil and
cell bodies in gray matter (spongiform change). The vacuolation
is accompanied by a variable degree of neuronal loss and
reactive gliosis, the degree of which increases with the duration of
the disease. Inflammatory infiltrates are usually absent.
CJD is characterized by rapidly progressive dementia, often
accompanied by gait abnormalities and startle myoclonus. The
disease is invariably fatal, with most patients succumbing within
about a year after the onset of symptoms.
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