All are features of Pertussis except –
Complications of Pertussis 
Respiratory -

Patchy Atelectasis
Subcutaneous emphysema
Pneumonia
Interstitial Pneumonia
Bronchiectasis
Pneumothorax
Otitis media

Neurological


Persistent seizures
Paraplegia                               
Ataxia
Hemiplegia
Convulsions & Encephalopathy

Gastro-Intestinal manifestation → Hernia & Rectal Prolapse

Hemorrhagic → Subconjunctival haemorrhage, Intracranial haemorrhage
Severe malnutrition
Although ataxia is seen in Pertussis, it is not of cerebellar origin. There is no involvement of the cerebellum in Pertussis (can you find any signs of cerebellar involvement in this pt. ie. Hypotonia, Intentional tremors. Nystagmus, scanning speech)
It is sensory ataxia.
Encephalopathy
Cerebellar Ataxia
Subconjunctival hemorrhage
Bronchiectasis