Leptomeningitis

What is Leptomeningitis?

Leptomeningitis can be defined as a medical condition, characterized by the inflammation of the subarachnoid space. Also known as meningitis, this condition affects both the arachnoid and the pia mater. Both infectious and non-infectious causes can be found behind the appearance of this health problem. However, it is important to remember that the infectious leptomeningitis is more common than the one caused by non-infectious causes. Bacterial infections can lead to the inflammation of the meninges, which is the protective membrane of the brain and spinal cord.

The infection can reach the protective membrane from other sites, such as the sinuses, middle ear or nose. Those who are between 30 and 50 years of age present the highest risk for developing leptomeningitis. In children, tuberculosis is the most common reason that leads to the appearance of such health problems.

What are the causes of leptomeningitis?

One of the most common types of leptomeningitis is the pyogenic one. In the elderly population, this condition is caused by the following infectious agents: streptococcus pneumoniae, listeria monocytogenes, neisseria meningitides and gram negative bacilli. The same form of leptomeningitis is caused by these particular infectious agents in adults, such as: streptococcus pneumoniae, neisseria meningitidis and group B streptococcus. In children, the main infectious agent is represented by neisseria meningitides. Both streptococcus pneumoniae and neisseria meningitides are responsible for the appearance of leptomeningitis in infants, while in neonates the following infectious agents are responsible: group B streptococcus, E. coli and listeria monocytogenes.

On the other hand, the viral meningitis is caused by enteroviruses. It is also possible to suffer from mycobacterial leptomeningitis, this form being caused by mycobacterium tuberculosis (tuberculous meningitis and tuberculous pachymeningitis). The fungal meningitis is caused either by cryptococcus neoformans (AIDS patients) and coccidioides immitis.

The aseptic leptomeningitis is caused by the following: leptomeningeal carcinomatosis, rheumatoid arthritis and sarcoidosis. Iatrogenic aseptic meningitis is encountered in the postoperative stage (regardless of the surgical intervention) and also in the situation of a hydrogel-coated aneurysm coils.

Pathophysiology

There are different factors that influence the localization, the extensiveness and the changes that occur at the level of the meninges. If the leptomeningitis has a middle-ear infection as cause, the lesion is going to be unilateral and most likely concentrated on the temporo-sphenoidal lobe. On the other hand, if the condition is caused by pneumonia or endocarditis, the meningitis is going to be bilateral and located at the level of the cortex. The exudate can be fibrinous, purulent or hemorrhagic. In children, it is characteristic for the ventricles to dilate. A turbulent fluid might also be present at the level of the meninges.

Leptomeningitis can also appear due to the hematogenous spread of a primary infection that is found at the level of the lungs. The infection can be acquired during birth – microorganisms in the birth canal. The aspiration of contaminated amniotic fluid can lead to leptomeningitis in newborns as well.

Symptoms of leptomeningitis

These are the most common symptoms of leptomeningitis:

• Headaches – severe and protracted
• Rigidity at the level of the neck
• Fever/chills – suggestive of the suppurative process
• Nausea and vomiting
• Intolerance to sound
• Delirium, followed by coma
• Slow pulse (it is only rapid in children)
• Affectation of the cranial nerves
  • Strabismus
  • Ptosis
  • Facial paralysis
  • Trophic changes (involvement of the 5th nerve)
• Convulsions – especially in children who present a nervous temperament

Pictures of Leptomeningitis

Leptomeningitis Picture 1 : Diagram showing the different parts of the Brain including Meninges, Cerebrum, Ventricles (fluid filled spaces), Skull, Cerebellum, Brain stem and Spinal cord.

Diagnosis

These are the most common methods used for the diagnosis of leptomeningitis:

• Medical history of the patient
  • Known infections and their causes
  • Previous treatments and/or surgical interventions
• Imaging studies
  • CT
    • No changes might be present on the scans
    • Liquid accumulation (subtle hydrocephalus)
    • The basal cisterns might present areas of hyperdensity around them
    • The leptomeningeal area might be enhanced
  • MRI
    • Leptomeningeal enhancement
  • MR angiography
    • The narrowing or occlusion of arteries can be identified.

Complications

These are the complications that can occur in patients suffering from leptomeningitis: thrombosis of the dural sinus, inflammation of the cerebral ventricles, accumulation of excess cerebrospinal fluid (hydrocephalus), infarction and abscess. Other complications include: edema, increased intracranial pressure, cranial nerve palsies and seizures.

Treatment

The measures of treatment are similar to the ones taken for other forms of meningitis.

Prognosis

Even though this is a serious condition, with the right treatment, it is not fatal.