Page 305 - Medicine and Surgery

P1: FAW
BLUK007-07 BLUK007-Kendall May 25, 2005 18:18 Char Count= 0

Chapter 7: Infections of the nervous system 301

compromise the arterial blood supply. The high pressure predisposition to streptococcal infection (e.g. asplenic
in small vessels may cause rupture and haemorrhage. patients), otitis media, alcoholism, skull fracture, neu-
rosurgery or immunosuppression.
Clinical features
Fever and headache are often features. Pathophysiology
Cortical vein thrombosis results in a stroke and The organisms may spread directly from the nasophar-

seizures. ynx, middle ear, the skull vault or haematogenously
Cavernous sinus thrombosis causes headache, fever then crossing the blood-brain barrier. Once within the

and eye signs (diplopia, proptosis, chemosis, opthal- cerebrospinal fluid (CSF), the bacteria multiply rapidly.
moplegia, papilloedema) which usually become bilat- There is an acute inflammatory response to the bacte-
eral. riawith neutrophils and cytokine release, then endothe-
Lateral venous sinus thrombosis has a sub acute on- lial dysfunction causing disruption of local blood flow,

set of fever, earache, headache, nausea and vomiting. oedema, and ischaemia and cell death. Hydrocephalus,
Papilloedema may be seen. This condition arises from raisedintracranialpressure,cranialnervepalsiesorother
mastoiditis and is now rare. neurological problems such as seizures may occur as a
Sagittal sinus thrombosis causes headache, papil- result. Neisseria meningitidis may cause meningitis, sep-

loedema, focal signs, confusion and epilepsy. ticaemia or both simultaneously.
Investigations
Clinical features
CT head may show occluded veins, oedema or haemor-
Meningitis should be considered in all patients with
rhage but is often normal, the best investigation is MRI
a headache and fever. Patients may have a prodromal
with venography (MRV). Investigations to identify un-
illness resembling ‘flu’.
derlying causes should also be performed.
The symptoms may progress rapidly over hours, or

afew days. The headache is generalised, and in-
Management
creases in intensity to severe. Associated symptoms in-
Anti-coagulation (despite evidence of haemorrhage),
cludephotophobia,confusionandnon-specificsymp-
anti-convulsant drugs and treat the underlying cause
toms such as malaise, nausea and vomiting, and neck
wherever possible.
pain.
Examination often demonstrates neck stiffness (an in-

Infections of the nervous ability to touch chin to chest passively or actively).
system Other signs of meningism are a positive Kernig sign
(when the hip is kept flexed at 90 , knee extension
◦
causes pain or is resisted) or Brudzinski sign (spon-
Meningitis and encephalitis taneous flexion of the hip when the neck is flexed).
Patients are examined for a petechial rash which sug-
Bacterial meningitis
gests N. meningitidis.
Definition There may be evidence of an underlying cause or ori-
Bacterial infection of the meninges (the tissues lining the gin for the infection.
brain and spinal cord).
Complications
Aetiology Neurological and cerebrovascular complications in-
The likely organism changes with age. In adults, the clude intracranial venous thrombosis, cerebral oedema
most common are Neisseria meningitidis, Streptococcus and hydrocephalus. Septic shock and disseminated
pneumoniae, and Haemophilus influenzae. Less common intravascular coagulation occur in 8–10% of patients
organisms include gram-negative bacilli (particularly as with meningococcal meningitis. N. meningitidis is also
a hospital acquired infection) and Listeria in the elderly associated with adrenal haemorrhage (Waterhouse–
andimmunocompromised.Predisposingfactorsinclude Friderichsen syndrome) which is rapidly fatal.