SELECT 
  a.category_id 
FROM 
  cscart_categories as a 
  LEFT JOIN cscart_categories as b ON b.category_id IN (554) 
WHERE 
  a.id_path LIKE CONCAT(b.id_path, '/%')

Query time 0.00040

Explain
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE b const PRIMARY,p_category_id PRIMARY 3 const 1
1 SIMPLE a ALL 214 Using where

Result

category_id
565
566
567
568
569
570
571
572
573
574
575
576
577