The body of ICMP TTL Expired messages must include the IP header of the original packet (which includes the source-port / destination-port) and 64 bits beyond the original header.
Based on timing and that header information, you can derive which packet triggered the TTL-expired message.
I am including a sample triggered by an NTP packet below...
See RFC 792 (Page 5) for more details.
ICMP TTL-Expired Message
Ethernet II, Src: JuniperN_c3:a0:00 (b0:c6:9a:c3:a0:00), Dst: 78:2b:cb:37:4c:7a (78:2b:cb:37:4c:7a)
Destination: 78:2b:cb:37:4c:7a (78:2b:cb:37:4c:7a)
Address: 78:2b:cb:37:4c:7a (78:2b:cb:37:4c:7a)
.... ...0 .... .... .... .... = IG bit: Individual address (unicast)
.... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
Source: JuniperN_c3:a0:00 (b0:c6:9a:c3:a0:00)
Address: JuniperN_c3:a0:00 (b0:c6:9a:c3:a0:00)
.... ...0 .... .... .... .... = IG bit: Individual address (unicast)
.... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
Type: IP (0x0800)
Internet Protocol, Src: 172.25.116.254 (172.25.116.254), Dst: 172.25.116.10 (172.25.116.10)
Version: 4
Header length: 20 bytes
Differentiated Services Field: 0x00 (DSCP 0x00: Default; ECN: 0x00)
0000 00.. = Differentiated Services Codepoint: Default (0x00)
.... ..0. = ECN-Capable Transport (ECT): 0
.... ...0 = ECN-CE: 0
Total Length: 56
Identification: 0x86d7 (34519)
Flags: 0x02 (Don't Fragment)
0.. = Reserved bit: Not Set
.1. = Don't fragment: Set
..0 = More fragments: Not Set
Fragment offset: 0
Time to live: 255
Protocol: ICMP (0x01)
Header checksum: 0xb3b1 [correct]
[Good: True]
[Bad : False]
Source: 172.25.116.254 (172.25.116.254)
Destination: 172.25.116.10 (172.25.116.10)
Internet Control Message Protocol
Type: 11 (Time-to-live exceeded)
Code: 0 (Time to live exceeded in transit)
Checksum: 0x4613 [correct]
Internet Protocol, Src: 172.25.116.10 (172.25.116.10), Dst: 172.25.0.11 (172.25.0.11)
Version: 4
Header length: 20 bytes
Differentiated Services Field: 0x00 (DSCP 0x00: Default; ECN: 0x00)
0000 00.. = Differentiated Services Codepoint: Default (0x00)
.... ..0. = ECN-Capable Transport (ECT): 0
.... ...0 = ECN-CE: 0
Total Length: 36
Identification: 0x0001 (1)
Flags: 0x00
0.. = Reserved bit: Not Set
.0. = Don't fragment: Not Set
..0 = More fragments: Not Set
Fragment offset: 0
Time to live: 0
[Expert Info (Note/Sequence): "Time To Live" only 0]
[Message: "Time To Live" only 0]
[Severity level: Note]
[Group: Sequence]
Protocol: UDP (0x11)
Header checksum: 0xee80 [correct]
[Good: True]
[Bad : False]
Source: 172.25.116.10 (172.25.116.10)
Destination: 172.25.0.11 (172.25.0.11)
User Datagram Protocol, Src Port: telindus (1728), Dst Port: ntp (123)
Source port: telindus (1728)
Destination port: ntp (123)
Length: 16
Checksum: 0xa7a1 [unchecked, not all data available]
[Good Checksum: False]
[Bad Checksum: False]