PE27.1-14 | Central Nervous System — Practice Quiz

Streptococcus pneumoniae is the most common bacterial meningitis pathogen in infants >1 month of age and older children. GBS dominates the neonatal period (<1 month). Hib was previously common but is now vaccine-preventable.

Bacterial meningitis pathogens are age-stratified: neonates = GBS + E. coli + Listeria; infants/children = S. pneumoniae + N. meningitidis. CSF neutrophilia, high protein, and glucose ratio <0.4 (22/88 = 0.25 here) indicate bacterial aetiology.

GBS (Group B Strep) is the leading cause in neonates <1 month old. Hib causes meningitis in the 1-month to 5-year age group but Streptococcus pneumoniae is now the most common overall after widespread Hib vaccination. Neisseria meningitidis is more common in older children and young adults.

Tuberculous meningitis (TBM) treatment per NTEP is 2HRZE (intensive phase, 2 months) followed by 10HR (continuation, 10 months) — total 12 months. Dexamethasone is added to reduce inflammation and mortality. Cobweb clot and lymphocytic pleocytosis with subacute onset are classic TBM features.

TBM triad: subacute onset (days to weeks), lymphocytic pleocytosis, CSF glucose ratio <0.5, protein >100 mg/dL, cobweb clot. Treatment: 2HRZE + 10HR (12 months total, per NTEP) + dexamethasone. TBM staging (Stages I-III) guides prognosis.

Ceftriaxone + vancomycin is for bacterial meningitis (neutrophilic, acute onset). Acyclovir is for Herpes simplex encephalitis (predominantly temporal lobe, HSV PCR positive). Amphotericin B + flucytosine is for cryptococcal meningitis (immunocompromised, India ink positive).

Bacterial meningitis: neutrophilic pleocytosis, glucose <40% of blood (CSF:blood ratio <0.4), high protein (>100 mg/dL), turbid. TBM: lymphocytic, very low glucose, very high protein, cobweb clot. Viral meningitis: lymphocytic, glucose usually normal, protein mildly elevated, clear CSF.

Memorise the CSF triad for each meningitis type: Bacterial (neutrophils, glucose <0.4 CSF:blood ratio, protein >100 mg/dL); TBM (lymphocytes, glucose very low, cobweb clot, protein 100-500 mg/dL); Viral (lymphocytes, glucose normal, protein mildly elevated 50-100 mg/dL).

The cell type and glucose levels clearly differentiate the three: bacterial = neutrophils + low glucose; TBM = lymphocytes + very low glucose + cobweb clot; viral = lymphocytes + normal glucose. Culture confirms but the initial CSF picture strongly guides empirical management.

The setting-sun sign (Parinaud's phenomenon in infants) results from the dilated third ventricle or tectal compression pressing on the dorsal midbrain (superior colliculi), causing impairment of upward conjugate gaze — the eyes appear tonically deviated downwards, showing a rim of sclera above the iris.

Hydrocephalus in infants presents with large head, bulging fontanelle, dilated scalp veins, and the setting-sun sign (downward eye deviation from dorsal midbrain compression). VP shunt is the primary treatment for obstructive hydrocephalus; ETV is an alternative in suitable cases.

Setting-sun sign is a specific neuro-ophthalmic sign of raised intracranial pressure compressing the dorsal midbrain conjugate gaze centre. It is not due to retinal detachment, papilloedema directly, or cortical blindness.

Simple febrile seizures (age 6 months to 5 years, generalised, <15 minutes, single episode per febrile illness, no neurological deficit) require only fever management and parental reassurance. Antiepileptic drugs are NOT indicated for simple febrile seizures. The prognosis is excellent.

Febrile seizures occur in 6 months to 5 years. Simple febrile seizures (generalised, <15 min, single in 24 h) require no AED. Complex febrile seizures (focal, >15 min, or recurrent in 24 h) need further evaluation. Risk of subsequent epilepsy is only slightly increased over the general population.

Antiepileptic drugs (phenobarbitone, levetiracetam) are not needed for simple febrile seizures. IV lorazepam is for status epilepticus (seizure ≥5 minutes). Lumbar puncture is not routinely required in children >18 months with a typical febrile seizure and no meningeal signs.

Carbamazepine is CONTRAINDICATED in childhood absence epilepsy (and juvenile myoclonic epilepsy). It may worsen absence seizures and myoclonic jerks by blocking sodium channels in a manner that exacerbates generalised epilepsy syndromes. First-line options are ethosuximide (pure absences) or valproate (absences + other generalised seizure types).

ILAE classifies epilepsy by seizure type, epilepsy type (focal/generalised/combined/unknown), and epilepsy syndrome. For childhood absence epilepsy: ethosuximide (first-line for pure absence) or valproate. Carbamazepine WORSENS absence and myoclonic seizures — a high-yield trap.

Ethosuximide is first-line for pure absence epilepsy (acts on T-type calcium channels in thalamus). Valproate is useful for absence + other generalised seizures. Lamotrigine is also effective for absence. Carbamazepine is the trap — it worsens absence and myoclonic seizures.

Status epilepticus is defined as a seizure lasting ≥5 minutes (operational definition). IV lorazepam 0.1 mg/kg is the first-line benzodiazepine for status epilepticus when IV access is available. It has a rapid onset and longer duration of action compared to IV diazepam.

Status epilepticus = seizure ≥5 minutes (operational) or two seizures without recovery. Management: ABC → IV/IO lorazepam 0.1 mg/kg → repeat if needed → phenytoin 20 mg/kg IV → phenobarbitone 20 mg/kg → ICU/anaesthesia. Time-to-treatment is critical.

Phenytoin 20 mg/kg is a second-line agent used when benzodiazepines fail. Sodium valproate IV is also a second-line option. Rectal paraldehyde is used when IV access is unavailable (out-of-hospital) or in resource-limited settings. Lorazepam IV is always first-line when IV access exists.

Spastic diplegia is the most common form of cerebral palsy, typically seen in preterm infants due to periventricular leukomalacia (PVL). Features include lower-limb predominant spasticity, brisk reflexes, Babinski sign, and preserved intelligence. Non-progressive motor disorder from a static brain lesion is the hallmark of CP.

Cerebral palsy: non-progressive motor disorder due to static brain lesion. Types by motor pattern: spastic (most common; diplegia in preterms, hemiplegia in term asphyxia, quadriplegia in severe injury), dyskinetic, ataxic, mixed. GMFCS grades functional mobility I-V.

SMA type II presents with hypotonia, absent reflexes, fasciculations — UMN signs are absent. DMD shows pseudohypertrophy, Gower's sign, elevated CK, X-linked. Hereditary spastic paraplegia is progressive with family history. The MRI finding of PVL strongly supports preterm-associated spastic diplegia CP.

This clinical picture (areflexia, tongue fasciculations, paradoxical breathing, preserved intelligence, no facial weakness) at 6 months is classic for SMA type I (Werdnig-Hoffmann disease) — a lower motor neuron disease. Deletion of SMN1 gene (on chromosome 5q) is confirmatory in ~95% of cases.

Floppy infant differential: central (brain) vs peripheral (LMN: SMA, neuropathy, NMJ, myopathy). LMN signs = areflexia + fasciculations + preserved consciousness; central = axial hypotonia, UMN signs. SMA type I (Werdnig-Hoffmann): onset <6 months, never sits, SMN1 deletion. New disease-modifying treatments (nusinersen, onasemnogene) are now available.

SMA is a peripheral (LMN) cause of floppy infant. Brain MRI cortical atrophy points to central (UMN) causes (CP, hypoxic-ischaemic encephalopathy). Elevated CK suggests myopathic disease (DMD, congenital myopathy). NCV showing sensorimotor neuropathy indicates peripheral neuropathy, not anterior horn cell disease.

Duchenne muscular dystrophy (DMD) is caused by mutations in the dystrophin gene on chromosome Xp21, inherited in an X-linked recessive pattern. Females are carriers; affected males show proximal muscle weakness, Gower's sign, calf pseudohypertrophy, and markedly elevated CK (10-100 times normal — 8500 U/L here = >40x).

DMD: X-linked recessive, dystrophin gene mutation (Xp21). Classic triad: proximal weakness + Gower's sign + calf pseudohypertrophy. CK 10-100x normal is the key lab marker. Diagnosis: CK + gene testing (deletion/duplication in 65% by MLPA; sequencing for point mutations). Steroids (prednisolone/deflazacort) are standard of care.

DMD is X-linked recessive. Autosomal dominant muscular dystrophies include facioscapulohumeral and myotonic dystrophy. Autosomal recessive includes limb-girdle MD type 2. Mitochondrial inheritance gives maternal transmission and predominantly affects high-energy tissues (brain, muscle, heart).