Additional information

1. Localizing signs: Brainstem strokes can be localized by recognizing the associated deficits caused by the involvement of specific cranial nerves as follows:

   III or IV cranial nerve: Midbrain lesion

   V cranial nerve: Rostral pontine lesion

   VI, VII, and VIII nerves: Caudal pontine lesion

   IX, X, and XII nerves: Medullary lesion (bulbar signs)

2. Parinaud’s syndrome: Also called dorsal midbrain or pretectal syndrome, it results from lesions in the area of the dorsal midbrain, most commonly pineal gland tumors, brainstem hemorrhage, and infarcts. It presents paralysis of vertical gaze, with a downward deviation of both eyes called the “setting sun” sign, along with dilated and fixed pupils, lid retraction, and nystagmus. Light reflex is lost, while accommodation reflex may or may not be lost. Light-near dissociation presents with poor bilateral pupillary constriction in response to light but preserved constriction with convergence. Vertical gaze palsy is due to damage to the vertical gaze center (rostral interstitial nucleus of the medial longitudinal fasciculus and the interstitial nucleus of Cajal and its connections. Collier sign or bilateral lid retraction is seen as the inhibitory supranuclear input to the III nerve nucleus is lost, leading to constant stimulation of the levator palpebrae superioris.

3. Pontocerebellar angle syndrome: It is seen in tumors or masses in the cerebellopontine angle like Schwanommas (acoustic neuromas), meningiomas, aneurysms, etc. It presents with tinnitus, loss of balance, sensorineural hearing loss, dizziness, vertigo, ataxia, and in late stages with ipsilateral facial weakness and paresis of muscles of mastication.

4. TIA: Transient ischemic attack is a transient stroke that lasts only a few minutes. It is caused by microembolization from an atheroscelrotic plaque. Most symptoms of a TIA disappear within an hour, although they may persist for up to 24 hours. Symptoms include numbness or weakness in the face, arm, or leg, especially on one side of the body; confusion or difficulty in talking or understanding speech; trouble seeing in one or both eyes; difficulty with walking; dizziness; or loss of balance and coordination.

5. Thalamic pain syndrome or Déjérine-Roussy syndrome: A lesion localized to the ventral posterolateral nucleus in the thalamus will lead to an initial loss of all sensations from the contralateral side of the body, including pain. Over time, the patient may experience pain in all or part of the contralateral side of the body. This is referred to as thalamic pain syndrome. About one-third of those who have a TIA will have an acute stroke sometime in the future. The most important treatable factors linked to TIAs and stroke are high blood pressure, cigarette smoking, heart disease, carotid artery disease, diabetes, and heavy use of alcohol.

6. Carotid artery stenosis: It is caused by atherosclerosis of the carotid arteries or, rarely, from fibromuscular dysplasia. It carries a high risk of causing stroke. It is asymptomatic in most cases. Symptomatic carotid artery stenosis presents with “amaurosis fugax”, contralateral weakness or numbness of an arm, leg or the face, dizziness, dysarthria and aphasia. Amaurosis fugax is due to cholesterol embolization from atherosclerotic plaques in the carotid artery to the retinal artery. It presents with sudden painless loss of vision (like a curtain coming down), eventually followed by restoration of vision (curtain raising up). Carotid bruits can be auscultated in carotid stenosis. Invasive treatment is considered for symptomatic patients with stenosis greater than 50% and asymptomatic patients with stenosis greater than 60%. Carotid endarterectomy, preferably within two weeks of symptoms, or carotid angioplasty with stenting are the preferred procedures. Asymptomatic patients are managed with medical therapy and lifestyle modifications.

7. Arteriovenous malformations of the brain: It is a developmental anomaly of blood vessels consisting of tangled, poorly formed blood vessels between a feeding artery and draining vein without a capillary network in between. It can cause SAH or intracerebral hemorrhage. It may cause seizures and neurological deficits and can be associated with aneurysms. They are most common in MCA territory. It has a characteristic “bag of worms” appearance on CT with contrast.

8. Posterior reversible encephalopathy syndrome: It presents with rapid onset of headache, seizures, altered sensorium, and visual deficits with reversible changes that resolve over days to weeks. It is associated with renal disorders like chronic kidney disease and acute kidney injury, hypertension, organ transplantation, immunosuppressive drugs, SLE, and TTP. It is postulated to result from loss of autoregulation of blood flow to the brain or systemic inflammation.

Risk factors for berry aneurysms.

Inherited risk factors

• Coarctation of aorta
• Polycystic kidney disease
• Ehler-Danlos syndrome
• Alpha 1 antitrypsin deficiency
• Alpha glucosidase deficiency
• Arteriovenous malformations
• Fibromuscular dysplasia
• Hereditary hemorrhagic telangiectasia
• Kleinefelter syndrome
• Noonan’s syndrome
• Tuberous sclerosis
• Family history of berry aneurysms

Acquired risk factors

• Hypertension
• Advancing age
• Atherosclerosis
• Cigarette smoking
• Cocaine, amphetamine abuse
• Head injury
• Infections

Normal CSF Findings

Abnormal CSF findings

* The CSF index is the CSF IgG to CSF albumin ratio compared to the serum IgG to serum albumin ratio. Any increase in the index reflects IgG production in the CNS. Raised CSF IgG index is seen in multiple sclerosis, neurosyphilis, SSPE, polyradiculopathy, etc.

** CSF glucose is normal in viral meningitis, neurosyphilis, and demyelinating diseases

*** Oligoclonal bands will be seen in CSF in multiple sclerosis (MS).

Common terms used to describe seizures

• Tonic: Muscles in the body become stiff
• Atonic: Muscles in the body relax
• Myoclonic: Short jerking in parts of the body
• Clonic: Periods of shaking or jerking parts on the body

13. Dandy Walker Syndrome: It is characterized by underdevelopment of the cerebellar vermis, cystic enlargement of the IVth ventricle and enlargement of the posterior cranial fossa. Causation is multifactorial, with few cases showing deletion of chromosome 3q, 6p,13q, or duplication of 9p. It affects more females than males. It presents with developmental delay, hypotonia or spasticity, mental retardation, seizures, poor coordination and balance (ataxia), and sometimes enlarged head circumference and increased pressure within the skull due to hydrocephalus. Severe cases may show respiratory failure. Imaging studies show classic mega-cisterna magna (enlargement of the cisterna magna).

14. Facial nerve (VII cranial nerve) palsy: Most cases are idiopathic. Known causes are Lyme disease, HSV, HZV, Coxsackie virus, Adenovirus, CMV, EBV, Measles, Mumps, Rubella and Influenza B viruses, head trauma, sarcoidosis, iatrogenic injury during surgery of the parotid gland, forceps delivery, etc. Swelling of the facial nerve from viral or immunological disorders can cause palsy.

    The motor nucleus of the VII nerve supplies the muscles of facial expression, stapedius, stylohyoid , and the posterior belly of the digastric muscle. The corticobulbar fibres arising from the motor cortex, provide bilateral innervation to the muscles of the upper face (involved in forehead wrinkling and shutting the eye), while they provide only contralateral innervation to the muscles of the lower face (involved in flaring of nostrils, mouth movements, smiling, etc.), via their respective facial motor nuclei. The facial nerve exits at the stylomastoid foramen and becomes extracranial.

    Patients with facial nerve palsy present initially with pain behind the ear, followed a few hours later by facial weakness and paralysis. Hyperacusis (hypersensitivity to loud sounds) is seen due to paralysis of the stapedius. Patients may be unable to show their teeth and their nasolabial folds flatten out. Ramsay Hunt syndrome is caused due to reactivation of VZV and presents with facial paralysis, herpetiform vesicular eruptions, and vestibulocochlear dysfunction. Depending on the location of the lesion, facial nerve palsy can be UMN or LMN. Idiopathic LMN facial palsy is also called Bell’s palsy.

15. Differentiating features between upper and lower motor neuron facial palsy

UMN or central facial palsy

• Lesion in cerebral cortex, internal capsule, corticobulbar fibres or cerebral peduncle etc, above the facial motor nucleus
• Contralateral paralysis of lower face, forehead is spared
• Forehead wrinkling maintained
• Can shut the eye
• Intact blink reflex
• Drooping of corner of mouth, contralateral to the lesion

LMN or peripheral facial palsy

• Lesion is distal to the facial nerve nucleus
• Ipsilateral upper and lower face paralysis
• Forehead wrinkling lost
• Cannot shut the eye
• Absent blink reflex
• Drooping of corner of mouth, ipsilateral to lesion