Background: Late infantile neuronal ceroid lipofuscinosis type 2 (CLN2) is a rare neurodegenerative disease that generally appears in children between 2 and 4 years old, leading to seizures and a progressive loss of language and motor functions. As the disease progresses, affected individuals typically experience blindness and ultimately pass away in late childhood. Treatment with intracerebroventricular cerliponase alfa has been shown to slow the deterioration of motor and language functions compared to the natural progression of the disease. We aim to highlight the early symptoms of CLN2 which help with early diagnosis and timely treatment initiation in children with specific medical indications, as well as identify medical contraindications for enzyme replacement therapy. Methods: We describe five Croatian patients and one Bosnia and Herzegovinian patient with CLN2 disease, analyzing the clinical characteristics, neuroimaging findings, electroencephalogram results, genetic analysis, treatment indications and contraindications, and disease progression. Results: All six patients presented with seizures: focal seizures (n = 1), myoclonic–atonic seizures (n = 1), febrile seizures (n = 2), and tonic–clonic seizures (n = 2), along with language delay (n = 6). Despite this, one patient refused treatment, two were initially included in the clinical trial and then continued treatment, one did not indicate starting treatment, and three continued treatment. One patient, after 4.5 years of treatment, no longer had medical indications for the therapy, which was discontinued. The other two patients who received treatment had a significant slowing of disease progression. Conclusions: The early onset of seizures between ages 2 and 4, alongside delayed language development, is a defining characteristic of CLN2 disease. Enzyme replacement therapy using cerliponase alfa represents the initial treatment for neuronal ceroid lipofuscinosis type 2, targeting the underlying cause of the disease. It effectively delays the progression of language and motor decline in patients diagnosed with this condition.