A 10 year old child presented with headache, vomiting, gait instability and diplopia. On examination he had papilledema and gait ataxia. The most probable diagnosis is –
Hydrocephalus
Brain stem tumour
Suprasellar tumour
Midline posterior fossa tumour
"The classical triad of headache, nausea and vomiting, and papilledenaa is associated with midline or infratentorial tumors".
 
Sign and symptoms of Brain tumors in children

Children with brain tumors frequently have symptoms and signs that strongly suggest the appropriate diagnosis.
The clinical triad of symptoms associated with increased ICT -4 headache, vomiting, blurred vision / diplopia, is the hallmark of brain tumors in childhood.
These symptoms occur more frequently with mid-line posterior fossa (infratentorial) tumors owing to the propensity of lesions close to the ventricular CSF flow system.
Symptoms of the brain tumors vary depending upon which part of the brain the tumor is found :­

Brain tumor in cerebrum (supratentorial)

Seizures                                 o Hemiperes is or Hemiplegia          o Drowsiness / confusion
Visual changes                     o T ICT (less common)                        o Personality changes

Brain tumor in brain stem

Seizures                                 o Diplopia             o Respiratory changes o T ICT (Rare)
Endocrine problem (DM) o Headache            o Cranial N. palsy

Brain tumor in cerebellum

T ECT (most common)     o Headache          o Uncoordinated movement
Vomiting                               o Ataxia

Symptoms due to raised ICT --> These are mainly caused by midline posterior fossa tumor --> Medulloblastoma.

Headache                                                    o Nausea                                                  o Drowsiness
Vomiting (usually in the morning)         o Personality changes                         o Papilledema
Diplopia / blurred vision                           o Irritability

Note - Brain-stem tumors are also posterior fossa tumors, but they do not present with increased ICT.