One-Liners for Pediatric Neurology

Important one-liners 

• Cerebral infarction can be caused by one or more of the following factors:
  • Inflammatory vascular obstruction
  • Thrombosis
  • Vasospasm

• Acute hydrocephalus is a feature of tubercular meningitis.
• However, when pyogenic meningitis is concerned, hydrocephalus is usually a long term complication.

Key points for complications in acute pyogenic meningitis

• Papilledema is not seen in uncomplicated acute pyogenic meningitis.
• If seen, it usually indicates a complicated case.
• If a child with meningitis has early onset hydrocephalus, weight loss, basal arteritis, or contact history, one must suspect that TB meningitis

Also read: Pediatric Oncology High Yield One Liners

Key one-liner facts to remember

• In neonatal CSF,0-32 cells, with 20-60% Neutrophils can be normal.
• In post-neonatal CSF, even a single neutrophil is significant.
• CSF-blood glucose ratio of < 0.4 has 80% sensitivity and 98% specificity for pyogenic meningitis.
• CSF Gram stain has 60% sensitivity, 90% specificity in pyogenic meningitis. Overall positivity is more for Pneumococcus (69- 93%) than Meningococcus (30-89%).
• CSF PCR studies are close to 100% specific if found positive in pyogenic meningitis.
• CSF pleocytosis with lymphocytic predominance may occur in very early pyogenic meningitis and neutrophilic predominance in very early aseptic meningitis.
• CSF pleocytosis is absent in severe overwhelming sepsis with meningitis and carries a poor prognosis.
• In partially treated meningitis, culture and Gram stain may be negative within 2-4 hours, but other parameters take days to normalize.
• PCR using broad-based bacterial 16S ribosomal RNA can be useful in partially treated meningitis patients.
• Bloody CSF can be traumatic, or due to HSV-meningoencephalitis.
• Traumatic CSF can have altered pleocytosis and proteins.
• CSF can be normal in early meningitis, especially in neonates. The test has to be repeated if required.
• Generally used CSF lactate cut-off is more than 35 mg/dL in pyogenic meningitis.
• More than 40 mg/dL serum CRP has 93% sensitivity and 100% specificity in clinically symptomatic patients.
• Normal CRP and normal procalcitonin carry a good negative predictive value close to 100%.
• If serum procalcitonin is more than 2 ng/ml, it can distinguish between bacterial and aseptic meningitis.
• Combination of Vancomycin and Meropenem has to be used if the patient is allergic to the penicillin group of antibiotics.

Points to Remember about TBM

• The onset of hydrocephalus is early compared to other CNS infections.
• The initial fever in stage 1 is usually subacute or insidious, but the onset of stage 2 is acute and dramatic.
• Higher Chances of CNS vasculitis, focal deficits, optic atrophy, and extrapyramidal complications than other CNS infections.
• Infants have more severe presentations.
• Nelson says: If any basilar meningitis + Hydrocephalus/ stroke/ CN Palsy → start ATT if no other cause is found.

Also read: Important Topics in Pediatric Neurology

Points to remember in Tuberculoma

• A tumor-like mass resulting from the aggregation of caseous tubercles resembles a brain tumor.
• Infratentorial in children, supratentorial in adults.
• Usually single, rarely multiple.
• It can produce fever, headache, vomiting, seizures, and FNDs.
• Associated with a positive Mantoux test, but CXR is normal.
• CECT/MRI: Extensive contrast enhancement with a ring-like pattern.
• Respond to ATT: Steroids are needed to decrease cerebral edema.

Syndromes Associated with CALM

• Ataxia telangiectasia
• Bloom syndrome
• Gorlin syndrome (Nevoid multiple Basal Cell Carcinoma Syndrome).
• Fanconi anemia
• Gaucher's disease and Hunter syndrome.
• NF-1 and sometimes in NF-2.
• Legius syndrome
• Maffucci syndrome
• McCune Albright syndrome
• Russell Silver syndrome
• Tuberous sclerosis

Follow-Up in TCS

• Brain MRI is done every 1-3 years.
• Renal imaging using ultrasound, CT, or MRI every 1-3 years.
• Echocardiogram is done every 1-3 yr in patients with cardiac rhabdomyoma.
• ECG is done every 3-5 years.
• HRCT chest, CT every 5-10 yr in females older than 18 years.
• Dental examination twice a year
• Skin examination once a year.
• Detailed ophthalmic examination annually in patients with vision concerns or retinal lesions.
• Regular early ophthalmic examination in a child receiving Vigabatrin.
• Neurodevelopmental testing at the beginning of 1st grade and screening for TAND at each clinic visit.

Also read: Congenital Erythropoietic Porphyria

Syndromes Associated with a Port Wine Stain

• Sturge Weber syndrome.
• Klippel-Trenaunay syndrome.
• Parkes Weber syndrome.
• Proteus syndrome.
• Cloves syndrome.
• Cobb syndrome.
• Beckwith-Wiedmann syndrome.
• Von Hippel-Lindau disease.
• Rubinstein-Taybi syndrome.
• Roberts syndrome.
• Coat disease.

Scoring Tool for Pediatric Migraine 

Pediatric Migraine Disability Assessment (PedMIDAS) In the past three months:

Q. How many full days of school did you miss because of a headache?

Q. How many partial days of school did you miss because of a headache?

Q. How many days did you go to school but functioned at less than one-half of your ability because of a headache?

Q. How many days were you not able to do things at home because of a headache?

Q. How many days were you not able to participate in other activities because of a headache?

Q. How many days did you participate in other activities but functioned at less than half your ability because of a headache?

NCV in GBS points to remember

• Two or more motor nerves should show characteristic findings: 
• AIDP
  • Slowing of motor and sensory nerve conduction velocity (less than 70% of the lower limit of normal values for age).
  • Prolonged distal latencies (>150%).
  • Conduction block (proximal to distal compound muscle action potential (CMAP) ratio <0.7).
  • Temporal dispersion of CMAP.
  • Increased F and H response latencies (>120% of the upper limit of normal).
• AMAN and AMSAN
  • Lack of neurophysiologic evidence of demyelination.
  • With reduced CMAP amplitude of motor and/or sensory nerve action potential (<80% of the lower limit of normal values for the age).

Also read: Pediatric Hematology Important Topics 

Likely Etiological Clues/Associations 

• Cerebellar Ataxia - Varicella Zoster virus
• Preceding /Accompanying diarrhea - Enterovirus
• Hepatitis: Coxiella burnetti
• Parotitis, Mild features -Mumps
• Chorioretinitis - CMV or WNV
• Dementia - HIV and Measles
• Extrapyramidal features the most common cause is JE, WNV, Nipah virus.
  • RTI features - Influenza or Adeno virus infections

MCQ Points from Nelson Textbook of Paediatrics (21st Edition) 

• Generalized Tonic-Clonic Seizure (GTCS) in 10-24% of the JE cases
• Extrapyramidal sequelae (common)
• Convalescent phase: 4-7 weeks after encephalitis phase
• Rapid fluctuations in CNS signs are characteristic of children with JE
• Symptom: Hyperreflexia sooner shifts to hyporeflexia.
• Some older patients develop cogwheel rigidity and resting (non-intention) tremors like in Parkinson's disease

MCQ Pearls 

• HSVE can cause recurrent aseptic meningitis called Mollaret meningitis.
• MERS: Mild Encephalopathy with Reversible Splenial lesion, a mild CNS dysfunction with multiple etiology. MERS is often triggered by infections caused by rotavirus, Salmonella, adenovirus, CMV, and influenza virus.
• The influenza virus has recently become the major cause of MERS. COVID-19 is a trigger of MERS.
• Possible pathogenic mechanisms of MERS are reversible infection-induced and autoimmune-induced that specifically target the splenium of the corpus callosum.
• Even without therapy, most of the patients show good prognosis without any sequelae.
• Complications: Many of the patients are associated with hyponatremia and few patients have increased IL-6 levels.
• MERS is not a true encephalitis but a triggered encephalitis

Also read: Important Topics for Pediatric Oncology Preparation

Remember for Superspeciality Exams 

Among newer antiepileptics, the following side effects and interactions need to be remembered

• Skin pigmentation and retinal degeneration: Retigabine and Ezogabine
• Stomatitis: Everolimus
• Hepatotoxicity with Valproate: Cannabidiol
• Maximum Interaction with other AEDs: Perampanel
• Homicidal and suicidal tendencies, aggression: Perampanel

Important questions for revision 

Q. A patient of DiGeorge syndrome develops pyogenic meningitis in the early part of infancy. What is the likely pathogen?

Ans. Listeria monocytogenes.

Solution:

• DiGeorge syndrome has thymic hyperplasia(T cell defects)
• T cell defects is associated with Listeria monocytogenes

Q. What is hypoglycorrhachia and why does it occur?

Ans. Hypoglycorrhachia is the condition when glucose in the CSF drops below 40-45 mg\dL. The most important mechanism is altered CSF transport of glucose across blood-brain barrier (due to decreased GLUT-1 due to inflammation)

• Increased glucose utilization (due to increased bacteria and inflammatory cells)
• Increased anaerobic metabolism

Q. Why does raised ICP occur in meningitis?

Ans.

• Raised ICP >30 cm H2O can occur in Pyogenic meningitis
• Cerebral Perfusion Pressure(CPP) is determined by Mean Arterial Pressure (MAP) - Intracranial pressure(ICP)
• ICP rises in patients with meningitis because of cerebral edema.
• Cerebral edema is caused due to:
  • Vasogenic edema (result of increased vascular permeability)
  • Cytotoxic edema (result of cell death)
  • Interstitial cerebral edema (result of increased hydrostatic pressure if there is an obstruction or problems in the absorption of CSF).

Q. What type of hydrocephalus is common in childhood meningitis?

Ans.

• Non-obstructive or communicating type of hydrocephalus is more common than Obstructive hydrocephalus
• Non-obstructive is more common because of decreased CSF absorption by arachnoid villi due to thick exudates.
• Obstructive (rare): It happens because of gliosis or fibrosis at the foramen of Magendie, foramen of Luschka or cerebral aqueduct.

Also read: High-Yield One-Liners on Genetic Disorders

Q. What are the consequences of raised ICP in meningitis?

Ans.

• If ICP is high, it causes reduction in CPP(Cerebral perfusion pressure)
• CPP = MAP - ICP
• This causes cerebral hypoperfusion, cerebral edema and cerebral death due to ischemia.
• However, structural displacement (For e.g.: Cerebellar tonsillar herniation) is not seen in raised ICP due to pyogenic meningitis, since the raised ICP is diffusely present in the entire subarachnoid space.
  • Transtentorial/Falcine herniation are rare

Q. A child empirically started on vancomycin plus ceftriaxone in appropriate dosage for acute pyogenic meningitis develops right upper quadrant pain and vomiting. What is the reason?

Ans. Ceftriaxone causes in children below 2 or 3 years biliary stasis of age, which leads to pseudolithiasis and biliary sludge formation. Biliary stasis is reversible and can be avoided with the use of cefotaxime.

Q. Why are seizures very common in neonates?

Ans.

• Delayed development or maturation of Na-K-ATPase in neonates.
• Increased density of N-methyl-D-aspartate receptors.
• Increased density of AMPA receptors, especially GLUR2 type (Ca+2 influx).
• Delayed development of GABAergic transmission.

Q. What is Electroclinical Dissociation or Uncoupling? 

Ans.

• Whenever there is seizure activity on EEG but no actual clinical seizure.
• Most of these patients are found to have underlying encephalopathy, but their significance is unclear.
• In general, the chances of uncoupling tend to develop adverse long-term neurological outcomes.

Q. Why Do Infantile Spasms Happen?

Ans. There are three processes involved, which can be singly or in combination.

• Increased corticotropin-releasing hormone (CRH).
• Sodium channels blockade.
• NMDA receptor stimulation.

Also read: Important Topics for Pediatric Nephrology 2025

Q. Which drug AED is used for bridge therapy?

Ans. Clonazepam.

• Rufinamide is also effective in many patients.
• Other modalities include ketogenic diets such as cannabinoids, corticosteroids and IVIG.
• Vagal nerve stimulation and Corpus Callosotomy for refractory drop attacks.
• Surgery can be a last resort.

Q. A 10-year-old boy is brought to you with complaints of delayed milestones. There are rhythmic movements involving hands and feet or abnormal crying, indicating laryngeal bleating-like movement produced by the child. The child has pallor and hyperpigmentation. What is the likely diagnosis?

Ans. Infantile tremor syndrome.

Q. A 3-year-old child developed HSV Encephalitis and was successfully managed and discharged. 6 weeks later, he presented with a recurrence of symptoms, this time with choreoathetosis and dyskinesias. What should be suspected?

Ans.

• It is likely relapsed, but the pattern of relapse was different
• So, it is post HSV infection causing Anti-NMDA-R Encephalitis.
  • HSV-1 infection can be a trigger factor for this Anti-NMDA-R Encephalitis.
  • In children, Age less than four years → prominent movement disorders are seen.
  • In an older child → behavioral disorders are seen.
  • Post-HSV can cause Anti-NMDA-R Encephalitis after 2-12 weeks of HSV infection.

Also read: High-Yield One Liners in Pediatric Pulmonology

Q. Name one condition with Polyminimyoclonus.

Ans. Spinal Muscle Atrophy

Q. Why does the same gene deletion produce DMD and BMD in different patients?

Ans. Because of the Reading Frame Rule, also called Monaco Rule. It states that the number of exons deleted is not the primary determinant of disease severity. There are two types of mutations which can be described due to deletion:

1. Out-of-frame mutation: Mutations producing altered reading frames (mRNA) will produce unstable truncated dystrophin, producing DMD.

2. In-frame mutations: Mutations with relatively preserved mRNA although it is semi-functional dystrophin, produce BMD. Rare mutations can also produce adult-onset quadriceps myopathy.

Q. A 4-year-old boy with a positive Gower sign and elevated CK is suspected to have Duchenne's muscular dystrophy. What is the next investigation to perform as a part of the diagnostic work-up?

Ans. Genetic testing

Swaimann says: “Mutation analysis of the DMD gene has largely replaced muscle biopsy as the first diagnostic test performed after serum CK testing”.

Q. Which is a new antiepileptic that has a high risk of homicidal, suicidal depression, and aggressive behavior-like features, especially if other CNS problems are present?

Ans. Perampanel

Q. What are the specific side effects, and why has the drug been withdrawn?

Ans. Hyperpigmentation can happen. Retinal toxicity leading to blindness can happen.

Q. Which is the newer anti-epileptic approved for use in the last five years and is useful as both monotherapy and adjuvant therapy in Dravet syndrome or Lennox-Gastaut syndrome?

Ans. Cannabidiol (because maximum evidence is available here in RCTs for use in Dravet syndrome or Lennox-Gastaut syndrome.

Also read: Frequently asked questions in Pediatric Cardiology

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