This is a follow up to our previous post, the 7 most devastating viral neurological infections. The list of bacteria that invade the nervous system is endless, but some stand out because of the fear they evoke, and the peril they pose. Here then are the 7 most horrifying bacterial infections that threaten the nervous system.
Many bacteria invade the covering of the brain, the meninges, without invading the brain substance. The commonest are Neisseria meningitidis, causing meningococcal meningitis, and Streptococcus pneumoniae, causing pneumococcal meningitis. Other relatively frequent meningeal intruders include Listeria monocytogenes and Haemophilus influenzae. Bacteria may get into the brain following infections elsewhere, such as sinusitis or otitis media (inner ear infection). There are many complications of bacterial meningitis such as cerebral venous thrombosis (CVT) and brain abscess.
Tuberculosis (TB) is probably as old as history. It is caused by mycobacterium tuberculosis, a slow groing but pernicious organism. TB spares no part of the nervous system, and manifests often as tuberculous meningitis (TBM) or Pott’s disease of the spine. Nervous system TB may also present as an encephalopathy, tuberculoma, brain abscess, vasculopathy, arachnoiditis, radiculomyelitis, and calvarial TB.
Treponema pallidum, the bacterium behind the dreaded syphilis, is another ancient bug. It has a variety of ways it terrorises the nervous system, and the longer it inhabits the neurones, the worse the outcome. Typical manifestations of neurosyphilis are tabes dorsalis, general paresis of the insane (GPI), taboparesis, stroke, meningovascular syphilis, optic neuritis (ON), and several movement disorders.
Lyme disease has acquired an infamy which is probably beyond its real notoriety. It is best known for its tick-borne transmission, and for its classical dermatological feature, erythema chronicum migrans. It affects the nervous system in diverse ways such as encephalomyelitis, lymphocytic meningitis, cranial neuropathies, spinal radiculitis, stroke, diaphragmatic paralysis, and peripheral neuropathy. Post-Lyme syndrome is a very contentious topic; you may read more on this in a post from our sister blog, The Neurology Lounge, titled ‘Why is chronic Lyme disease so frustrating to neurology.
Neurobrucellosis is a rarely discussed bacterial infection but it is a significant contributor to neurological morbidity and mortality around the world. It is caused by various brucella species usually grouped under the name Brucella militensis. It has a long reach in the nervous system, causing a variety of insults such as encephalitis, meningoencephalitis, cranial neuropathies, intracerebral haemorrhage (ICH), subarachnoid haemorrhage (SAH), transverse myelitis, radiculitis, and peripheral neuropathy.
This most distasteful of infectious diseases unfortunately has a strong affinity for the nervous system. Unlike its distant cousin, TB, leprosy favours the peripheral over the central nervous system. Its hallmark is thickening of the nerves or nerve hypertrophy. Caused by Mycobacterium leprae, leprosy has a legion of neurological manifestations such as mononeuritis, mononeuritis multiplex, cranial and peripheral neuropathy, myelitis, and leprous ganglionitis.
Botulism is the end result of damage by the toxin of Clostridium botulinum. This toxin produces a deadly paralysis by blocking neural transmission across the neuromuscular junction (NMJ). Botulinum toxin respects no borders, able to gain access to the nervous system through the gut, the skin, or the lungs. It paralyses everything, causing acute limb, ocular, and bulbar weakness. Left unchecked, botulism results in autonomic dysfunction and respiratory failure.
PS: For Tetanus, check out The Neurology Lounge blog post on The 13 most dreadful neurological disorders
Explore more neurological infections in neurochecklists!